《韩非子·难势》
慎到说：飞龙乘云飞行，腾蛇乘雾游动，云雾一旦消散，它们就如同蚯蚓、蚂蚁一样了，因为它们失去了腾空飞行的凭借。
慎子曰：飞龙乘云，腾蛇游雾，云罢雾霁，而龙蛇与蚓蚁同矣，则失其所乘也。
Shen Dao said: A flying dragon rides on the clouds and flies, a flying snake rides on the mist and travels, and once the clouds and mist scatter, they will be the same as earthworms and ants because they have lost what they rely on for flying.