Friar Luca Pacioli, Divina Proportione, Venice, 1509 (RV F.V.44)

 "... having, with the diligence worthy of the enterprise, already completed a book on painting and human movement…": This passage, taken from a letter addressed to Ludovico Sforza from Luca Pacioli and printed in "Pars prima" of his Divina Proportione (On the Divine Proporton) is among the earliest evidence of Leonardo's work on a Book of Painting.  Pacioli was a "compatriot" and friend of Leonardo, whom he met in Milan in 1496 when he was called by Duke Ludovico il Moro to teach mathematics. When he wrote the Divina Proportione, which originated, as we learn from the dedication of the work, from the scientific conversations within the extraordinary milieu that was the court of Ludovico il Moro and to which also Leonardo belonged, he felt the need to complete the text with geometric diagrams. For this task he drew on the skills of Da Vinci, whose original drawings he kept in order to display them for the admiration of visitors.