When the three worlds were in darkness, Vishnu slept in the middle of the cosmic ocean. A lotus grew out of his navel. Brahma came to him and said, ‘Tell me, who are you?’ Vishnu replied, ‘I am Vishnu, Creator of the Universe. All the worlds, and you yourself, are inside me. And who are you?’ Brahma replied, ‘I am the Creator, and everything is inside me.’ Vishnu then entered Brahma’s body and saw all three worlds in his belly. Astonished, he came out of Brahma’s mouth and said, ‘Now, you must enter my belly in the same way and see the worlds.’ And so Brahma entered Vishnu’s belly and saw all the worlds. Then, since Vishnu had shut all the openings, Brahma came out of Vishnu’s navel, and rested on the lotus.
-Kurma Purana 1.9, written around the 8th century CE
