《梦溪笔谈·讥谑》
过去除授太子中允这一官职的人极少，只有久为幕职官而不得提拔、累积了较高资格的人才以这一官职安置，所以被任命为此官的多是仕途潦倒不得志之人。
旧日官为中允者极少，唯老于幕官者。累资方至，故为之者多潦倒之人。
In the past, very few people were appointed to the position of Crown Prince's Secondary Officer. Only those who had served as staff officers for a long time but had not been promoted, and had accumulated high qualifications, could be appointed to this position. Therefore, most of those who were appointed to this position were people who had not been successful in their careers.