Aitareya Upanishad 1.1

In the beginning this was but the absolute Self alone. There was nothing else whatsoever that winked. He thought, "Let Me create the worlds."

He created these worlds, viz ambhas, marīci, mara, āpaḥ. That which is beyond heaven is ambhas. Heaven is its support. The sky is marīci. The earth is mara. The worlds that are below are the āpaḥ.

He thought, "These then are the worlds. Let Me create the protectors of the worlds." Having gathered up a (lump of the) human form from the water itself, He gave shape to it.

He deliberated with regard to Him (i.e. Virāṭ of the human form). As He (i.e. Virāṭ) was being deliberated on, His (i.e. Virāṭ's) mouth parted, just as an egg does. From the mouth emerged speech; from speech came Fire. The nostrils parted; from the nostrils came out the sense of smell; from the sense of smell came Vāyu (Air). The two eyes parted; from the eyes emerged the sense of sight; from the sense of sight came the Sun. The two ears parted; from the ears came the sense of hearing; from the sense of hearing came the Directions. The skin emerged; from the skin came out hair (i.e. the sense of touch associated with hair); from the sense of touch came the Herbs and Trees. The heart took shape; from the heart issued the internal organ (mind); from the internal organ came the Moon. The navel parted; from the navel came out the organ of ejection; from the organ of ejection issued Death. The seat of the procreative organ parted; from that came the procreative organ; from the procreative organ came out Water.footnote{Thus originated the presiding deities of the organs from the limbs of Virāṭ.}