梦溪笔谈
The later Song Dynasty scientist Shen Kuo (1031–1095 CE) used the models of lunar eclipse and solar eclipse in order to prove that the celestial bodies were round, not flat. This was an extension of the reasoning of Jing Fang and other theorists as early as the Han Dynasty. In his "Dream Pool Essays" of 1088  CE, Shen related a conversation he had with the director of the Astronomical Observatory, who had asked Shen if the shapes of the Sun and the Moon were round like balls or flat like fans. Shen Kuo explained his reasoning for the former: