This is the frontispiece of Procli Diadochi by Francesco Barozzi, published in Venice, 1560. Barozzi (1537 - 1604) was a Venetian nobleman, a mathematician, astronomer and humanist. A correspondent of Christopher Clavius, he was well known in the Italian mathematical community of the time. He was a translator of and commentator on ancient mathematical classics and was particularly active in the 16th century movement to revive an interest in Euclidean geometry. His book is a translation of and commentary on Proclus Diadochus’ ( 411 - 485 ) edition of Euclid's Elements. The portrait depicts Barozzi.
A discussion of parallel lines from Procli Diadochi, pages 214 - 215. Barozzi was noted for devising fourteen different methods for constructing a set of parallel lines.