Plimpton 322 is an ancient Babylonian tablet that has been only now deciphered after a great deal of effort. It turns out, it is a remarkably accurate trigonometric table! This breaks the record for both the oldest and the most accurate ancient table of its kind.
Some of the difficulty in deciphering the old mathematical reference comes from the fact that the ancient Babylonians counted in base 60. (This is, in fact, the reason we use numbers like 360 and 180 to describe angles. They are were nice round numbers to the Babylonians!)
To learn more about this fascinating discovery, check out the original paper which is available as a free download as long as you are using a computer on the CofC campus.