《后汉书·本纪·孝和孝殇帝纪》
十年春三月二十八日，诏令说： 堤防沟渠，是用来理顺帮助地理，使障塞通达。
十年春三月壬戌，诏曰： 堤防沟渠，所以顺助地理，通利壅塞。
On the 28th day of the 3rd month of the 10th year (May 1, 169), an imperial edict stated, "Dike embankments and irrigation canals are designed for the regulation of geographical features and for the facilitation of access.