Euclid's Elements of Geometry. Book page with Latin text and diagrams from the first printed edition (Venice, 1482) of Euclid's 'Elements of Geometry'. Euclid (active 300 BC) was one of the most influential Greek mathematicians. The thirteen books of his 'Elements of Geometry' organised the work of many previous Greek geometricians as well as containing new discoveries that Euclid had made himself. Euclid attempted to establish a fully rigorous system in which each theorem was proved on the basis of its predecessors, having as a starting point a set of self-evident axioms. This page shows propositions 19 to 22 (plus title for 23) from Book I.