clepsydra at the Beijing drum
tower consists of a series of vessels positioned in sequence at
different elevations, from which water trickles down through taps,
while at the base is a cylindrical vessel with a measuring rod that
would rise with the water level and indicates the time. On the side
stands a bronze, mechanical, mandarin-like figurine holding a set of
cymbals, that would be activated by an overflow mechanism every 15
minutes and clap the cymbals (fig.).