This is the frontispiece of *Procli Diadochi* by Francesco Barozzi, published in Venice, 1560. Barozzi (1537 - 1604) was a Venetian nobleman, 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 the edition of Euclid's *Elements* by Proclus or Proclus Diadochus (411 - 485), a manuscript known simply as *Procli Diadochi*. 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.