So... just how big are tomestones?

[Atoli]

They are more like mini memory cards in terms of "how much data they can hold" than a piece of paper, (as in, the data is stored, not inscripted) from what I understand, so size doesn't really matter
Even if they are reeeaally tiny, they can still hold a lot of information.

Then again...
I've seen lots of people say "they must be tiny because we can carry 8000 of them around at once" but I think we have established by now that we have magical pockets that allow us to carry around a lot more than it would be possible