"Famous people, famous words" is an educational series from 1996, presenting a number of famous persons, both Chinese and foreign, and their famous utterances. Zhang Heng (张衡, 78-139 CE) was a astronomer, mathematician, seismologist, hydraulic engineer, inventor, geographer, cartographer, ethnographer, artist, poet, philosopher, politician, and literary scholar from Nanyang who lived during the Later Han dynasty. He is best known for the first seismograph for measuring earthquakes that he invented in 132. The device was made of copper, in the shape of an egg with eight dragon heads around the top, each with a copper ball in its mouth, and a pendulum in the centre. Around the bottom were eight frogs, each directly under a dragon head. When an earthquake occurred, a ball fell out of a dragon's mouth into a frog's mouth, making a noise. In fact the seismograph detected an earthquake in February of 138 and Zhang reported this fact to the Emperor despite no other evidence of the earthquake being felt in the capital. He was even able to indicate that the earthquake was to the west of the capital. He achieved fame when reports of an earthquake more than a thousand kilometres northwest reached the capital several days later.
This quote from Zhang reads: "Living diligently, everything can be achieved" (人生在勤，不所何获).