Tao Te Ching: Chapter 70
My words are very easy to know, and very easy to practise; but there is no one in the world who is able to know and able to practise them.
There is an originating and all-comprehending (principle) in my words, and an authoritative law for the things (which I enforce). It is because they do not know these, that men do not know me.
They who know me are few, and I am on that account (the more) to be prized. It is thus that the sage wears (a poor garb of) hair cloth, while he carries his (signet of) jade in his bosom.