《淮南子·本经训》
不说话的辩才、不能具体规定的 道 ，如若有人能通达这种境界，那就叫做进入到天府，这里面取之不尽，用之不竭，无法知道它产生的缘由，这就是瑶光。
不言之辩，不道之道，若或通焉，谓之天府。取焉而不损，酌焉而不竭，莫知其所由出，是谓瑶光。
Eloquence with no words, a  path  that cannot be defined - if someone can reach this kind of realm, it is called entering the Heavenly Treasury. Within it, there is no end, no depletion, and it is impossible to know its origins. This is called Yao Guang.