Guo Shoujing

Also known as Zi Ruosi · Shun De · Zhao Wen Guan Da Xue Shi · Zhi Tai Shi Yuan Shi

Guo Shoujing, courtesy name Ruosi, came from Xingtai in Shunde; his grandfather, versed in mathematics and water control, sent him to study under Liu Bingzhong. Recommended by Zhang Wenqian in 1262, he laid six irrigation and canal proposals before Khubilai and was put in charge of the empire's waterways. When the court set out to reform the calendar in 1276 he and Wang Xun divided the work of observation and computation; he built more than a dozen instruments, among them the simplified armillary and the tall gnomon, and sent observers to twenty-seven stations from Goryeo to Hainan to measure the sun's shadow. The new system, named the Shoushi calendar, was issued in 1280. In 1291 he proposed bringing the Baifu spring water through Wengshan Lake into Dadu as a grain canal; finished in 1293, it was named the Tonghui River by Khubilai. He died in 1316 at eighty-six. Emperor Chengzong, after a flood Guo had warned of, called him a divine man.