“The tao that can be told
is not the eternal Tao
The name that can be named
is not the eternal Name.
The unnameable is the eternally real.”

Source: Tao Te Ching, Ch. 1, as translated by J.H.McDonald (1996) http://www.wright-house.com/religions/taoism/tao-te-ching.html [Public domain translation]
Context: The tao that can be described
is not the eternal Tao.
The name that can be spoken
is not the eternal Name.
The nameless is the boundary of Heaven and Earth.
The named is the mother of creation.
Freed from desire, you can see the hidden mystery.
By having desire, you can only see what is visibly real.
Yet mystery and reality
emerge from the same source.
This source is called darkness.
Darkness born from darkness.
The beginning of all understanding.

Source: Tao Te Ching, Ch. 1, as interpreted by Ursula K. LeGuin (1998)
Context: The way you can go
isn't the real way.
The name you can say
isn't the real name.
Heaven and earth
begin in the unnamed:
name's the mother
of the ten thousand things.
So the unwanting soul
sees what's hidden,
and the ever-wanting soul
sees only what it wants.
Two things, one origin,
but different in name,
whose identity is mystery.
Mystery of all mysteries!
The door to the hidden.

¶ 6-7.
An Humble, Earnest and Affectionate Address to the Clergy (1761)
Context: All possible goodness that either can be named, or is nameless, was in God from all eternity, and must to all eternity be inseparable from him; it can be nowhere but where God is. As therefore before God created anything, it was certainly true that there was but one that was good, so it is just the same truth, after God has created innumerable hosts of blessed and holy and heavenly beings, that there is but one that is good, and that is God.
All that can be called goodness, holiness, divine tempers, heavenly affections, in the creatures, are no more their own, or the growth of their created powers, than they were their own before they were created. But all that is called divine goodness and virtue in the creature is nothing else, but the one goodness of God manifesting a birth and discovery of itself in the creature, according as its created nature is fitted to receive it. This is the unalterable state between God and the creature. Goodness for ever and ever can only belong to God, as essential to him and inseparable from him, as his own unity.

The Death of the Duke of Clarence and Avondale

Source: Dictionary of Burning Words of Brilliant Writers (1895), P. 83.

These notes were possibly written in preparation for a letter. The meaning is obscure.
The Notebooks of Leonardo da Vinci (1883), XIX Philosophical Maxims. Morals. Polemics and Speculations.

Source: Tao Te Ching, Ch. 25, as translated by Ch'u Ta-Kao (1904)