《明史·志·卷一》
也是二百五十里相差一度。用周天的度数来计算，得知地的全周是九万里。
以周天度计之，知地之全周为九万里也。
It is also a difference of one degree every two hundred and fifty li. Calculating using the degrees of the celestial sphere, we learn that the Earth's circumference is ninety thousand li.