Transcription: Leonardo filled one folio at a time and that allowed him to maintain some kind of control. I could imagine Leonardo sitting at a desk with five or six or seven different notebooks of different periods in front of him and going through it and culling notes on one subtopic to fill a folio and then another subtopic to fill another folio and if those folios got messy in the process of this culling to rewrite them and some of the folios in this treatise are so neat we know that they could be first drafts. They must be things that Leonardo wrote and rewrote.
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