he was born in 1231 in xingtai, hebei province. his family was poor. he grandfather, guo yong, was famous for his study of the five classics to astronomy, mathematics, and hydraulics. guo shoujing was a child prodigy. as a teenager, he learned how to build a water clock. he then improved it. his new invention was called the lotus clepsydra (a bowl shaped like a lotus flower that water dripped into). at 16 he began to study math and from there hydraulics and astronomy.