The Upanishads, Part 1 (SBE01), by Max Müller, , at sacred-texts.com
1. The northern rays of the sun are the honey-cells on the left. The (hymns of the) Atharvâṅgiras are the bees, the Itihâsa-purâna 1 (the reading of the old stories) is the flower, the water is the nectar.
2. Those very hymns of the Atharvâṅgiras (as bees) brooded over the Itihâsa-purâna; 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.
39:1 As there is no Atharva-veda sacrifice, properly so called, we have corresponding to the Atharva-veda hymns the so-called fifth p. 40 Veda, the Itihâsa-purâna. This may mean the collection of legends and traditions, or the old book of traditions. At all events it is taken as one Purâna, not as many. These ancient stories were repeated at the Asvamedha sacrifice during the so-called Pariplava nights. Many of them have been preserved in the Brâhmanas; others, in a more modern form, in the Mahâbhârata. See Weber, Indische Studien, I, p. 258, note.