In 422, Emperor Mingyuan suffered a major illness, apparently caused by medicines that alchemists had given him that were supposedly capable of extending lifespans. He consulted Cui Hao on what he should do to prepare for events after his death. Cui Hao predicted that he would recover, but advised him to create his oldest son, 14-year-old Tuoba Tao the Prince of Taiping, crown prince, and then transfer some of the authorities to the crown prince so that his own burdens could be lessened. The senior official Baba Song (拔拔嵩) also agreed, and Emperor Mingyuan created Tuoba Tao crown prince, and further had Crown Prince Tao take the throne to serve as the secondary emperor. He commissioned his key advisors Baba, Cui, Daxi Jin, Anchi Tong (安遲同), Qiumuling Guan (丘穆陵觀), and Qiudun Dui (丘敦堆) to serve as the Crown Prince's advisor. From this point on, most matters, particularly domestic matters, were ruled on by Crown Prince Tao, while Emperor Mingyuan himself only ruled on important matters. It was at this time that Emperor Mingyuan made positive remarks about each of the officials that he so charged with advising the crown prince, and as to Cui Hao, he stated, "Cui Hao is exceptionally knowledgeable and able to discern the will of Heaven and men."