This is a virtue which grants a single supernatural ability - The Language of memory. Unlike other abilities, this cannot be improved by exposure or practice.
The language of memory lets you write down a single memory using the special symbols of the language. Anyone who has this virtue can "read" your writing and create their own exact copy of the memory.
A single memory about something would take up an entire page from a book. A more detailed memory (or a duration longer than momentary) would need multiple pages.
The memory can contain any of the 5 senses, each sense adds more detail. The memory can contain information about an ability or language, but these are more complex matters needing a lot of planning and writing. As it is usually hard to separate knowledge, a person would write their entire knowledge of a subject in large block. After reading the complete block, all of that knowledge is gained.
Incomplete blocks only give fragments of a memory and conflicting information.
If a person has prior knowledge about a subject before reading one of these books they will need to make concentration rolls after the final page has been read. These concentration rolls determine if there are any conflicts between the new memories and the old ones.
Level 1 of the ability lets you write a single memory onto a single page.
Level 2 lets you use more complicated symbolism so you can put two memories onto a page.
Each additional level doubles the amount you can write in the same space.
A person cannot read information above their ability level - if they have level 1, they cannot read memories written using level 2.
The advantage of higher levels is that memories can be written more swiftly.
Higher levels can only be taught by someone who knows them. The current highest known level is 9 which was created by the founder. There are a few sets of tractati which introduce each level of the language.
We were playing around with numbers about how many pages were needed for 1XP of an ability, we were eventually looking at around 20 pages of LM 1 for 1 XP of an ability or art.
Level 5 in an ability (75XP) would take 1500 pages of LM1.
If a person already has level 4 in an ability they would still need to read all 1500 pages and pass a concentration roll to absorb the extra information.
The Language of Memory was created so that knowledge could be transferred in its entirety. It was created to preserve knowledge incase of a cataclysmic disaster such as a second schism war.
The Language of Memory is useful with Mental Construct laboritories because objects can be described using LM and transferred to other magi for use in their lab.
A magus with LM 9 could write 256 memories onto a single page. 6 pages could allow them to write 75XP worth of knowledge (1500 memories). These 6 pages can only be read by a person with LM 9 or higher
We weren't sure if we should follow the normal rules for reading text / writing text.
When magi have LM 9 it allows them to read and write memories very efficiently, they can exchange and learn knowledge very quickly - but the knowledge is the same. They cannot gain XP from reading a book the other wrote. It would be like reading a book they wrote themselves.
LM can be saga changing, summae would lose some value but tractati would become more precious.
One of the benefits of LM is to pass memories of events - especially for witnesses to a Hermetic Crime. People involved in such cases could have their memories transcribed in LM so that even if they die their testimony will remain.