[Design of Marci Letter]

[Jorge_Stolfi]

parchment books had been made from hides before that for many centuries, and hides came in non-normalised (but also non-uniform) sizes.

What surprised me in that plot was how close the aspect ratios are to the A4 ratio of sqrt(2) = 1.414... 

I think it shows that the aspect ratio of traded sheets was standardized, if not their sizes. If the original ratio was, say , 1 (square) or 2, the halved and quartered sheets would have one of those two ratios.  An original aspect ratio of phi = 1.618... would give books with aspect ratios alternating between ~1.62 or ~1.24. 

The reason I showed the plot is that there is almost a continuum of sizes even in this small sample of herbal books. Your plot also shows that clearly.

I can understand that people with deficient pareidolia could see it that way.  I see many clusters...

Someone in that thread stated that they had done a much more extensive survey.  I haven't checked that yet.  Did they consider this question? Like looking for regional size standards (French, German, Italian, ...), or vellum x parchment?

All the best, --stolfi