To prove the truth of the celestial sphere theory, the Eastern Han dynasty astronomer Zhang Heng (78-139 AD) designed a water-driven celestial globe. Water dripping from a clepsydra (a vessel with a small hole from which water drips at a constant rate) drove a train of gears to move a globe, representing the sphere of heaven, through one revolution per day, in time with the movement of the heavens.
東漢天文學家張衡為了證明「渾天說」的正確性，曾經設計了一架「漏水轉渾天儀」，以漏壺的流水為動力，通過齒輪系統，帶動象徵天殼的渾象一天旋轉一周，好讓它剛好吻合天象。