《论衡·卷二十九·对作篇》
古代有派使臣到各地采集民诗的事情，这是君王想以此来了解各地风俗和老百姓的情况。
古有命使采爵，欲观风俗知下情也。
In ancient times there were envoys sent to various places to gather folk songs, which was the monarch’s way of understanding local customs and the people’s situation.