“Only by knowledge of that which is not thyself, shall thyself be learned.”

All and Everything: Views from the Real World (1973)
Context: There do exist enquiring minds, which long for the truth of the heart, seek it, strive to solve the problems set by life, try to penetrate to the essence of things and phenomena and to penetrate into themselves. If a man reasons and thinks soundly, no matter which path he follows in solving these problems, he must inevitably arrive back at himself, and begin with the solution of the problem of what he is himself and what his place is in the world around him. For without this knowledge, he will have no focal point in his search. Socrates’ words, “Know thyself” remain for all those who seek true knowledge and being.

Card XXI : The World
The Symbolism of the Tarot (1913)
Context: The vision disappeared as suddenly as it appeared. A weird silence fell on me. "What does it mean?" I asked in wonder.
"It is the image of the world," the voice said, "but it can be understood only after the Temple has been entered. This is a vision of the world in the circle of Time, amidst the four principles. But thou seest differently because thou seest the world outside thyself. Learn to see it in thyself and thou wilt understand the infinite essence, hidden in all illusory forms. Understand that the world which thou knowest is only one of the aspects of the infinite world, and things and phenomena are merely hierolgyphics of deeper ideas."

Source: Aphorisms and Reflections (1901), p. 164

Card II : The High Priestess
The Symbolism of the Tarot (1913)
Context: Then the woman turned her face to me and looked into my eyes without speaking. And through me passed a thrill, mysterious and penetrating like a golden wave; tones vibrated in my brain, a flame was in my heart, and I understood that she spoke to me, saying without words:
"This is the Hall of Wisdom. No one can reveal it, no one can hide it. Like a flower it must grow and bloom in thy soul. If thou wouldst plant the seed of this flower in thy soul — learn to discern the real from the false. Listen only to the Voice that is soundless... Look only on that which is invisible, and remember that in thee thyself, is the Temple and the gate to it, and the mystery, and the initiation."

Encyclopedia of the Philosophical Sciences (1816)

The last address of King Dominicus Corea (Edirille Rala) on the gallows in Colombo before he was executed by the Portuguese - as quoted in:

Vol. 2, Ch. 1, § 1
Parerga and Paralipomena (1851), Counsels and Maxims

Letter to Farkas Bolyai (2 September 1808)
Context: It is not knowledge, but the act of learning, not possession but the act of getting there, which grants the greatest enjoyment. [Wahrlich es ist nicht das Wissen, sondern das Lernen, nicht das Besitzen sondern das Erwerben, nicht das Da-Seyn, sondern das Hinkommen, was den grössten Genuss gewährt. ] When I have clarified and exhausted a subject, then I turn away from it, in order to go into darkness again. The never-satisfied man is so strange; if he has completed a structure, then it is not in order to dwell in it peacefully, but in order to begin another. I imagine the world conqueror must feel thus, who, after one kingdom is scarcely conquered, stretches out his arms for others.