Zhang Sixun

Zhang Sixun (simplified Chinese: 张思训; traditional Chinese: 張思訓; pinyin: Zhāng Sīxùn; Wade–Giles: Chang Ssu-hsün, fl. 10th century) was a Chinese astronomer and military engineer from Bazhong, Sichuan during the early Song Dynasty (960-1279 AD). He is credited with creating an armillary sphere for his astronomical clock tower that employed the use of liquid mercury (dripped periodically from a clepsydra clock). The liquid mercury filled scoops of the waterwheel would rotate and thus provide the effect of an escapement mechanism in clockworks and allow the astronomical armillary sphere to rotate as needed. He designed the model for his armillary sphere in 976 and completed the creation of it in 977.