Zhang Heng. He was (AD 78–139) a Chinese astronomer, mathematician, inventor, geographer, cartographer, artist, poet, statesman. He lived under the Han Dynasty (AD 25–220) of China. He was a Chief Astronomer, Prefect of the Majors for Official Carriages, and then Palace Attendant at the imperial court. He invented the world's first water-powered armillary sphere, improved the inflow water clock by adding another tank and invented the world's first seismometer, which discerned the cardinal direction of an earthquake 500 km away. He improved previous Chinese calculations of the formula for pi. In addition to documenting about 2,500 stars in his extensive star catalogue. Some modern scholars have also compared his work in astronomy to that of Ptolemy (AD 86–161). (Adapted from Wiki)
A replica of an ancient Chinese Siesmograph (25-220 CE). Picture taken in July 2004 at Chabot Space & Science Center in Oakland California.
"In 132 CE, after several serious earthquakes in China, astronomer Zhang Heng invented this instrument to warn people of the next one. When the ground shook, it moved a pendulum inside the jug. The pendulum pushed a lever that opened one dragon's mouth. A ball rolled out and into the toad's mouth below, sounding an alarm. The open dragon mouth pointed in the direction of the earthquake, notifying the Emperor."