The idea of calculating fractional pawns of Vis came from an examination of the book economy of the Order of Hermes; its' beginnings are as a (pardon the pun) bookkeeping convention. It is not suggested that fractional pawns are usable for enchantment, or study, or spellcasting, or other magical pursuits; just that they are used to accurately account for the value of other things which are not Vis. No breakthrough is needed.
If someone wants to use the fractional pawns for magic instead of economics, then they will need a pile of them. Or, as you say, a single fraction & a Breakthrough based on Soqotan magic -- although I think the Soqotans use thirds of a pawn, and we are talking about fourths or fifths here.
The issue comes in when you are physically dealing with them (coins containing Vis) rather than writing about them (economics ledger).
Without some breakthrough then there is no way to make fractional "Vis Coins" that actually contain some fraction of a pawn of Vis. The Pawn is the smallest unit of Vis Hermetic Magic can currently interact with. You need a breakthrough to split them smaller.
Do you have a citation for that? I think it is widely assumed, and mages tend to stick with pawns as the smallest unit because it is the smallest magically-useful unit, but I (and it could just be me) cannot recall it being explicit in the rules.
Looking into it more and reviewing old threads, I actually am at a tossup. While there are fractional sources of Vis is early books (50 pairs of bat wings to a pawn in an early Covenant) there is no clarity on if Hermetic Magic can manipulate fractions anywhere. What I mean by this is if it can be used to manipulate the Vis in 10 pairs of bat wings (0.2 pawns total) or fails with less than 50 pairs. Also after that early period the books moved to whole pawns in an object per source (that I could review in the time since your post).
There is also no clarity on if you take multiple fractions of raw sources of Vis you can actually get a usable pawn from them (from say 25 pairs of those bat wings and half a badger liver in which a whole one contains a pawn). While they are both the same Form, they are not the same Vis.
All actual Hermetic usage of Vis must be in whole pawns by the rules though.
This makes it a YSMV point on if Hermetic Magic can manipulate fractional quantities of Vis or not. It also makes it a YSMV point if Hermetic Magic can use a mixed group of fractional Vis from different sources as a whole Pawn. If you wish to use those assumptions in your Saga then that is perfectly fine.
It can actually lead to more complications in tracking Vis. In a game that is already extremely complex though I am generally against things that add more complexity without a major upside.
IIRC the canonical covenant of Semita Errabunda has a vis source that is sackfuls of bird poop containing a 2 pawns Auram vis. They have to collect "virtually all of it" to gain the pawns. However if a sack of poop contains 1 auram vis it stands to reason that half a sack contains half a pawn. Though the text is also very explicit that they need to collect all of the poop to get the vis implying that hermetic magic cannot really deal in halves of vis.
though the inference is not nearly as strong as an explicit statement to that effect would have been.
Semita Errabunda is one of the "early books" I looked at when I was doing a quick review for my post. While I (obviously) fall into the camp that Hermetic Magic cannot really deal in halves of Vis I can see where some groups might go the opposite way. I do not believe this is something that the writers are actually very interested in clearing up, since there are several post in older threads that straddle the "maybe... possible..." line.
That inference you reached combined with the writers posts is the driving force in why I leaned strongly towards YSMV.
Add to the pile of 'this is a toss up, and something that needs to be decided by the troupe...' is The Mysteries (Revised Edition) Page 40: ReVi 25 "Divide the Gathered Essence" which includes the sentence 'The maga may freely choose how the Vis is to be divided." Of course, the prefacing paragraph describing the utility of the spell makes no mention at all of fractional pawns. The spell also leaves vague the point of whether or not the distribution of Vis is limited by the size & material of the receptacles -- I tend to think that the common sense answer is 'Yes, size and material affect capacity', but that is not strictly how this spell is written.
I can throw a bunch of examples. Lab rat who doesn't expect to come across vis in the world. Anyone in a summer+ covenant where they have items to measure and locate vis. There's a bunch of magi who would expect other people in the covenant to deal with that....
Or, perhaps it's not actually the bird droppings, but the act of gathering it that makes the Vis appear?
And if you don't "finish the ritual" (collect virtually all the droppings), it fails to work?
That may well be the case but nonetheless the text is IMO pretty clear that the vis is contained within the droppings. I have posted a quote of the relevant piece of text, as I believe it makes my point clear beyond doubt.
The guano deposited by birds on the covenant itself yields two pawns of Auram vis every year. Virtually all of it needs to be collected to get the vis, which is normally transferred to another vessel. Neither col- lection nor transfer are popular jobs.
reading this, I see no other possible interpretation than that the poop itself is where the vis actually is. This leaves us with the question of what happens if you divide the poop evenly into 4 containers, since logically each ought to contain half a pawns worth of vis. IMO the most likely option is that the half pawns worth of vis in poop is detectable as concentrated auram vis by hermetic magic (e.g. spells that detect magical residue) but if you try to measure it with a spell that counts pawns of vis, the spell fails to detect any pawns.
Re: the items, as I said - or something similar. Not that I think having 1 enchanted item at the covenant as being the same as having the spell. If the character has a personal item, sure. But unless you're taking redcap virtues, it's not as designing a magi starting with items is normal - you design your magi with spells, items come with the covenant. As to magi not expecting to ever encounter vis, or expecting other people to deal with that, how can I put this? If you're designing a character that doesn't expect to ever adventure, study from vis, use vis in the lab or cast a ritual spell, and never exchange vis with your sodales, you're designing an odd magi. Now I'm sure there are ways to be sufficiently organized to keep stocks of what your pawns are in which items, but it's handy not to have to carry a ledger of your owned vis, all sorted out in different boxes or items so as to be recognizable since you can't verify it's value, and to go back to the premise of this thread, it's really handy to be able to count your money, because that's what vis is to magi, and having to rely on someone else to count vis is next level dysfunctional in my mind. Not that you couldn't decide to skip the spells and rely on spontaneous magic, of course, but it's not something I would usually want to be doing.
How do you think the nobles of mythic europe feel? Most of them are relying on servants and advisors to tell them what their money is worth, as they have no feel for the precious metal content of coins, or if they've been clipped. The new idea of "double entry book-keeping" - putting in the ledger how much you paid for something and how much you got for it, to make sure you don't sell at a loss unless forced to - is by no means universal in 1220. "Beyond dysfunctional" economics go with the medieval setting, which is why studying intellego is so rewarding.
I think it's likely that the average shilling is worth a shilling and the average pence is worth a pence, and neither are likely to be found in a dead animal body, growing on a tree, or be blown by the northern wind. I also think the average shilling has the shape of an average shilling, whereas some vis pawns are carried in a pawn, others might be carried in a rock, a coin, or a cut rabbit's foot. Which makes the later all the more important to assess, because while mythic europe does have a fair number of coin types, minting rights are still somewhat relatively central enough that it's not the mess it would be if every trader minted their own coin.
I think you are overselling their importance. If I find vis on an adventure, who cares how much it is worth or what it is, if someone can work it out later? Unless one is in a ridiculously vis heavy game, it's rare to use vis picked up on the fly to boost a spell. Most vis is lab work.
In the modern day many people depend on accountants. In the medieval era the noble always had a functionary to deal with their money. Having a magi accountant in the covenant is a reasonable option.
One can trust the magi in the covenant who is measuring the vis, as let's think what happens if the accountant magi lies and skims vis. The accountant magi is drummed out of the convenant, his reputation in tatters, the moment it is found out.
I appreciate character design is what it is, so getting those 2 spells is less than 10% of your spell level allocation. I dislike the meta of it.
For a moderate selection of magi, it just does not fit the way they would approach the world. Many characters have a certain direction, a drive, a focus. Considering the low spell count an early mage has, especially if they want a few level 30+ spells in their main area, even 10 levels spent elsewhere can be too much.
Most young magi will have at least one, if not more, senior magi around them. It would be expected the senior magi would deal with vis and sometime later the magic can learn the InVi spells.
One can trust the magi in the covenant who is measuring the vis, as let's think what happens if the accountant magi lies and skims vis. The accountant magi is drummed out of the convenant, his reputation in tatters, the moment it is found out.
There is also the tiny matter that 'stealing magical power' is a Hermetic High Crime.
Depending on how the Saga is set up, someone will have to bite the bullet on them most likely. Though it doesn't have to come down to "Bob it is your turn to play the accountant this Saga". An actual fairly easy way around it is to assign some Lab Text during Covenant creation. 10 levels is worth 2 BP and they are definitely spells that should be in most decent libraries. For medium power you are looking at 1.3% of their average BP total (775). For low power games they are expensive, but then everything is expensive.
While it is YSMV, you will find many SG including ones running games on this board have posted Scales of the Magical Weight (InVi 5), Sense of Magical Power (InVi 2), and Sense the Nature of Vis (InVi 5) are spells every Magus should learn early in their life. Many young Magi have a decent chance of being able to learn all of them in a single season if they have text.
I had always interpreted "...Virtually all of it needs to be collected to get the vis..." as meaning the Vis was only present when all the guano was collected in one place. Separate the guano (eg putting in 4 equal amount containers) and you don't have any Vis at all.
Perhaps the separated piles will give the signature of having recently been in contact with Auram Vis.
What is the medieval paradigm of saying something is "quantum" related? Until all the guano is collected, the Vis won't collapse/crystalise out of the local Aura, and it is only loosely attached to the guano, so that it re-sublimates if the nucleation center falls below a critical threshold.
If a giants eye contains 2 pawns of vis, cutting in half, a pawn each or is the magic destroyed? I'd suggest vis destroyed, or at least the magi have a small time to move the vis to another recepticle using magic.
Caveat: Pure opinion. I have no idea what the canonical interpretation is.
