Caption: Euclid (fl. 300 BCE) in a detail from The School of Athens (1509--1511).

The hair-challenged Euclid is giving the totally-engaged and luxurously hirsute students a lesson in geometry.

Hipparchus (c.190--c.120 BCE) and Ptolemy (c.100--c.170 CE) are about to drop globes on Euclid.

The model for Euclid was Donato Bramante (1444--1514) (see Wikipedia: The School of Athens: Program, subject, figure identifications and interpretations).

Credit/Permission: Raphael (1483--1520), 1510--1511 (uploaded to Wikipedia by User:Cyberpunk, 2006) / Public domain.
Image link: Wikipedia: File:Euclid.jpg.
Local file: local link: euclid.html.
File: Ancient Astronomy file: euclid.html.