Ring/Circle, drawing, orientation

Can't find it right now, but there was a thread about circles recently. If my specific question was already answered a pointer would be great.

Anyway, as far as I remember it's pretty clear a circle has to be painted horizontally, but does it have to be painted on a horizontal surface?

What I have in mind specifically is painting the circle on the wall, like in a line that fully goes around a circular room or building (either inside or outside).

Wouldn't that just be an extreme case of painting the circle on top of a cornice?

I can't see any problems there.


Actually, that's not the case.
A circle need not be "painted", but only traced.
And it can be placed on surfaces that are not horizontal, not static, not rigid: Covenants has magic circles drawn on book pages, for example.

That earlier thread was one I was in a lot. I think there's a lot of 'decide how to interpret this', with a lot of examples, possible interpretations, and people arguing for or against various interpretations.

I think this was the thread.