This is the title page of Isaac Barrow’s (1630-1677) Euclide's Elements, 1660 edition. Barrow was self-taught in geometry. He originally published this book in 1655 as a simplified version of the Elements. It became very popular, and for the next half century was the standard English language text on the subject.
Below are pages 10 and 11 of Barrow’s Euclide's Elements. The illustration on page 11 presents Euclid's proof of Proposition I.5 (The base angles of an isosceles triangle are equal). This is the Pons Asinorum [Bridge of Asses] of medieval geometry. If one could prove this proposition, he or she was considered a competent mathematician.