In the city of Hangzhou, not far from Baoshi Mountain on the north bank of West Lake, there is a small road called Xixi Road (Xixi means West Brook), and toward the eastern stretch of this road, between the Yuquan and Xixi campuses of Zhejiang University, but closer to the Xixi campus, there is a stone bridge known as Daogu Bridge. It was first built during the Jiaxi period of the Southern Song dynasty (1237–1241); at that time, it was called Xixi Bridge. In the Lin’An Chronicles, written in the early years of the Southern Song Xianchun period, there appear about it the following remarks: “The Xixi Bridge, east of the examination courtyard of Lin’an Prefecture (Hangzhou) was built by Daogu during the Jiaxi period of the Song Dynasty.” The man who built this bridge, referred to here by his nickname Daogu, was none other than Qin Jiushao, the great mathematician of Southern Song.