《资治通鉴·梁纪·梁纪一》
汉灵帝光和元年，南宫寺的母鸡快变成公鸡了，只有头上的冠子还没变，灵帝就这件事诏问议郎蔡邕，蔡邕回答说： 头是元首，是皇帝之象征。
灵帝光和元年，南宫寺雌鸡欲化为雄，但头冠未变，诏以问议郎蔡邕，对曰： 头为元首，人君之象也。
In the first year of the Emperor Han Lingdi’s Guanghe reign, a hen at the Nangong Temple had almost transformed into a rooster, with only its crest remaining unchanged. Emperor Lingdi summoned and asked Master of Imperial Documents Cai Yong about this matter. Cai Yong responded: “The crest is the head, which symbolizes the emperor.”