Aitareya Upanishad

We are told: “Before creation, all that existed was the Self, the Self alone. Nothing else was. Then the Self thought: “Let me send forth the worlds.”

He sent forth these worlds: Ambhas, the highest world, above the sky and upheld by it; Marichi, the sky; Mara, the mortal world, the earth; and Apa, the world beneath the earth.

He thought: “Behold the worlds. Let me now send forth their guardians.” Then he sent forth their guardians.

He thought: “Behold these worlds and the guardians of these worlds. Let me send forth food for these guardians.” Then he sent forth food for them.

He thought: “How shall their be guardians and I have no part in them? If, without me, speech is uttered, breath is drawn, eye sees, ear hears, skin feels, mind thinks, sex organs procreate, then what am I?”

He thought: “Let me enter the guardians.” Whereupon, opening the centre of their skulls, he entered. the door by which he entered is called the door of bliss.”