《汉书·纪·文帝纪》
五月，下诏令说： 古代治理天下，朝廷门前设有进善言的旌旗，立有批评的柱板，是为了使上下通达而广开言路。而当今的法律有 诽谤妖言 之罪，这就使得众臣不敢做到知无不言与言无不尽，而皇上也就无法听到过失了。
五月，诏曰： 古之治天下，朝有进善之旌，诽谤之木，所以通治道而来谏者也，今法有诽谤、訞言之罪，是使众臣不敢尽情，而上无由闻过失也。
In May, the edict was issued: in ancient times, the flag of encouraging kind words and the pillar for criticism were set up at the palace gate, with an aim to bring superiors closer to their inferiors and to open the road for words. But given the current law of “slandering with sorcery”, most of my subjects dare not express their opinions openly, which has made it impossible for me to hear about my errors.