“Geometry has two great treasures: one is the Theorem of Pythagoras, the other the division of a line in extreme and mean ratio. The first we can compare to a mass of gold; the other we may call a precious jewel.” —Mysterium Cosmographicum, Johannes Kepler
Johannes Kepler (1571–1630) was a German mathematician and astronomer best known for his laws of planetary motion. As a mathematician, Kepler studied the golden ratio—which he referred to as the extreme and mean ratio—and has compared it to a precious jewel, which inspired this website’s name. He declared the golden ratio together with the Pythagorean theorem as geometry’s “two great treasures”. Ironically, Kepler compared the Pythagorean theorem to a “mass of gold”, which would have been more appropriate for the extreme and mean ratio since this is now popularly known as the golden ratio.