Geometry has two great treasures: one is the Theorem of Phythagoras, 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.Johannes Kepler, translation of Karl Fink in Geschichte der Elementar-Mathematik (1890) in A Brief History of Mathematics (1903) Beman, W.W. & Smith, D.E., transl., at an unspecified page.