《明史·志·卷七》
到时，徐光启率领钦天监大臣预点日晷，调整壶漏，用测高仪器测量食甚时日晷的高度。
至期，光启率监臣预点日晷，调壶漏，用测高仪器测食甚日晷高度。
At that time, Xu Guangqi led the ministers of the Imperial Astronomical Bureau to pre-point the sundial, adjust the water clock, and use the altimeter to measure the height of the sundial at the time of the solar eclipse.