In the ancient world, sundials were used to measure time but it would work only with sunlight, and they could not maintain a constant division of time. To compensate for these shortcomings, the water clock was invented. The oldest known example is dated to 1500 BC, and is from the tomb of the Egyptian pharaoh Amenhotep I. Here is a an example found in the tomb of Ramesses VI. The presence of a pharaoh with an erect penis is not explained, but the phallus is always a symbol of power, nothing to be ashamed of ^^