From 《
楚辞·
渔父》(Chu Ci, The Fisherman, ca. 3rd c. BCE), the Fisherman's reply to Qu Yuan:
沧浪之水清兮,
可以濯我缨;
沧浪之水浊兮,
可以濯我足 (When Canglang's water is clear, I wash my hatstrings; when it is muddy, I wash my feet).
缨 = the silk tassels of an official's hat, symbol of office; washing them requires pure water, i.e., an honorable regime. A Daoist argument for adapting to the times instead of destroying oneself for principle. Also quoted in 《
孟子·
离娄上》as a children's song that Confucius overheard and commented on.