The oldest printed illustration of a water clock (clepsydras) in any culture, from a Sung edition of the Liu Ching T'u of Yang Chia (c A.D. 1155), enlarged by Mao Pang-Han (c. A.D. 1170). On the right, a drawing of the archaic inflow type of camp clepsydra described in the Chou Li, with a torch beside it to ward off the frost. On the left, "Mr. Wang's lotus clepsydra", i.e., the design of Wang P'u (c. 1135), which includes an overflow tank and an occlusive indicator-rod.