Opening from Pacioli’s De Viribus Quantitatis, folios 259v-260r, Biblioteca Universitaria, Bologna, codice n. 250.
I began with this account of nature printing by Luca Pacioli from his De Viribus Quantitatis (On the power of numbers) and started printing from leaves.
To learn how to reproduce single leaves, chiefly those with veins
That is, those which have ribs or veins, such as the leaves of violets, lesser celandine, grapevine, sage, stonecrop, ox-tongue or roses.
Take finely ground charcoal, or lampblack which is used to print books, and is much better. Mix it well, adding common oil, then with a sponge or brush spread it on a clean surface in a thick layer. Then take your leaf, well cleaned, put it vein side down on to the inked surface, and put a clean sheet of paper carefully on top of the leaf. Then press the paper with your hand or fingers, but not too hard, as the leaf should not be broken. Once the leaf is coated with black, put it on to another white sheet of paper, taking care it does not move. Then put another sheet of paper over it, and apply some pressure to it: the black impression you want will stay on the paper. It will look very good, but only the outlines will be seen; then with verdigris or some other green water colour paint it carefully and it will look very natural, as you will see.
I used ready-made oil-based printing ink and polyurethene ink rollers to ink both sides of the leaf and pressed it [using another roller] between sheets of Zerkall mould made paper.