《魏书·列传·卷九》
元禧忧愁急迫不知怎么办，对龙虎说： 我烦乱不能忍受，你试作一个谜语，我当思虑破解，来消除烦闷。 
禧忧迫不知所为，谓龙虎曰： 吾愦愦不能堪，试作一谜，当思解之，以释毒闷。 
Yuanxi was full of anxiety and urgency, not knowing what to do, so he said to Longhu: I cannot endure this unrest. Try to make an enigma, which I will ponder to solve, for it will relieve my boredom.