The Da Vinci Notebooks at sacred-texts.com
On draperies (390--392).That part of a fold which is farthest from the ends where it is confined will fall most nearly in its natural form.
Every thing by nature tends to remain at rest. Drapery, being of equal density and thickness on its wrong side and on its right, has a tendency to lie flat; therefore when you give it a fold or plait forcing it out of its flatness note well the result of the constraint in the part where it is most confined; and the part which is farthest from this constraint you will see relapses most into the natural state; that is to say lies free and flowing.
196 Let a b c be the fold of the drapery spoken of above, a c will be the places where this folded drapery is held fast. I maintain that the part of the drapery which is farthest from the plaited ends will revert most to its natural form.
Therefore, b being farthest from a and c in the fold a b c it will be wider there than anywhere else.
200:196 13: a c sia. In the original text b is written instead of c--an evident slip of the pen.
200:197 : See Pl. XXVIII, No. 6, and compare the drawing from Windsor Pl. XXX for farther illustration of what is here stated.