Tao Te Ching: Chapter 15
The skilful masters (of the Tao) in old times, with a subtle and exquisite penetration, comprehended its mysteries, and were deep (also) so as to elude men's knowledge. As they were thus beyond men's knowledge, I will make an effort to describe of what sort they appeared to be.
Shrinking looked they like those who wade through a stream in winter; irresolute like those who are afraid of all around them; grave like a guest (in awe of his host); evanescent like ice that is melting away; unpretentious like wood that has not been fashioned into anything; vacant like a valley, and dull like muddy water.
Who can (make) the muddy water (clear)? Let it be still, and it will gradually become clear. Who can secure the condition of rest? Let movement go on, and the condition of rest will gradually arise.
They who preserve this method of the Tao do not wish to be full (of themselves). It is through their not being full of themselves that they can afford to seem worn and not appear new and complete.