《三国志·魏书·任城陈萧王传》
青龙三年，曹楷因为派属官到中尚方官署制造禁物而被治罪，被削去两千户食邑。
青龙三年，楷坐私遣官属诣中尚方作禁物，削县二千户。
In the third year of the Qinglong era (235 CE), Cao Kai was convicted of sending a subordinate official to the Imperial Palace to manufacture prohibited objects, and 2,000 households of his fief were stripped from him.