《汉书·传·眭两夏侯京翼李传》
《尚书》说 历象曰月星辰 ，这是说可以仰观天象，俯察地理，观察曰月的运行，望星辰的排列，度量山的变动，考察民谣民俗，用来制定法度，考求祸福。
《书》曰： 历象日月星辰 ，此言仰视天文，俯察地理，观日月消息，侯星辰行伍，揆山川变动，参人民谣俗，以制法度，考祸福。
The Book of Documents says: "According to the document on the observation of astronomical phenomena, the sun, moon and stars …" This means that one can look up and observe the heavenly bodies and look down and observe the geography, observe the movements of the sun and moon, study the arrangement of the stars, calculate the changes in the mountains, and investigate popular songs and customs, in order to work out laws and ordinances, and assess fortune and disaster.