Nachiketas:
How, O King, shall I find that blissful self, supreme, ineffable, who is attained by the wise? Does he shine by himself, or does he reflect another’s light?
King of Death:
Him the sun does not illumine, nor the moon, nor the stars, nor the lightning – nor, verily, fires kindled upon the earth. He is the one light that gives light to all. He shining, everything shines.
This universe is a tree eternally existing, its roots aloft, its branches spread below. The pure root of the tree is Brahman, the immortal, in whom the three worlds* have their being, whom none can transcend, who is verily the Self.
Katha Upanishad
*(The sky, the earth, and the nether world)
Unanimous Tradition / Tradición Unánime 