《魏书·帝纪·卷八》
当初，高祖欲检查诸子的志趣风尚，便大摆宝物，任听各个儿子拿取，京兆王元愉等全都竞相选取珍宝玩好，世宗只是挑了一个骨制如意而已。
初，高祖欲观诸子志尚，乃大陈宝物，任其所取，京兆王愉等皆竞取珍玩，帝唯取骨如意而已。
At the beginning, Emperor Gaozu wanted to check his sons' ambition and style, so he displayed the treasure and let his sons choose it, King Jingzhao, Yuan Yu and others all chose precious treasures and toys, but Emperor Shizong only chose a bone wishful thinking.