Pacioli was a Italian renaissance mathematician, born in 1445 in Sansepulcro, Tuscany.... He wrote De divina proportione (On the Divine Proportion), a book on mathematics, illustrated by Leonardo da Vinci, composed around 1498 in Milan and first printed in 1509. It has been said that he taught mathematics to Leonardo de Vinci. In this disputed but famous work, the table is filled with geometrical tools: slate, chalk, compass, a dodecahedron model, and his own Summa and a work by Euclid. A rhombicuboctahedron half-filed with water is suspended from the ceiling. Pacioli is demonstrating a theorem by Euclid. Detail shows rhombi-cuboctahedron, which could not be executed more exactly It has been said that the artist complicated his task by showing it half full of water and showing the consequent reflections and refractions.. Some have said the other man might be Albrecht Durer. See http://www.ritrattopacioli.it/texting.htm for a discussion of the attribution of this painting.