Guo Shoujing
In 1231, in Xingtai, Hebei province, China, Guo Shoujing was born into a poor family. He was raised primarily by his paternal grandfather, Guo Yong, who was famous throughout China for his expertise in a wide variety of topics, ranging from the study of the Five Classics to astronomy, mathematics, and hydraulics. Guo Shoujing was a child prodigy, showing exceptional intellectual promise. By his teens, he obtained a blueprint for a water clock which his grandfather was working on, and realized its principles of operation. He improved the design of a type of water clock called a lotus clepsydra, a water clock with a bowl shaped like a lotus flower on the top into which the water dripped. After he had mastered the construction of such water clocks, he began to study mathematics at the age of 16. From mathematics, he began to understand hydraulics, as well as astronomy.