Euclid's Elements
Galileo's Lectures on Dante's Inferno
Galileo's Discovery of Scaling Laws, Am. J. Phys. 70 (2002), 575.
A Renaissance application of trigonometry.
A nice look at the vanishing point.
A nice site on geometrical optics.
How Simple Harmonic motion is related to circular motion.
Geoffrey West's KITP talk on the fractal model of the vascular system
