Diagram of the eye from Margarita philosophica by Gregor Reisch (1467-1525) was a German Carthusian humanist writer. His chief work is the Margarita philosophica, which first appeared at Freiburg in 1503. It is an encyclopedia of knowledge intended as a textbook for students, and contains in twelve books Latin grammar, dialectics, rhetoric, arithmetic, music, geometry, astronomy, physics, natural history, physiology, psychology, and ethics. The usefulness of the work was increased by numerous woodcuts and a full index.