Khandogya-Upanishad: Third Prapathaka, Fourth Khanda
1. The northern rays of the sun are the honeycells on the left. The (hymns of the) Atharvangiras are the bees, the Itihasa-purana (the reading of the old stories) is the flower, the water is the nectar.
2. Those very hymns of the Atharvahgiras (as bees) brooded over the Itihasa-purana; and from it, thus brooded on, sprang as its (nectar) essence, fame, glory of countenance, vigour, strength, and health.
3. That flowed forth, and went towards the sun. And that forms what we call the extreme dark (parah krishnam) light of the sun.