Book XV: 3.13-14

Now the Persians do not erect statues or altars, but offer sacrifice on a high place, regarding the heavens as Zeus [Ahura-Mazda]; and they also worship Helios [the Sun], who they call Mithras, and Selene [Anahita or the Moon] and Aphrodite, and fire and earth and winds and water; and with earnest prayer they offer sacrifice in a purified place, presenting the victim crowned, and when the Magus, who directs the sacrifice, has divided the meat the people go away with their shares,...; but still, according to some writers, they place a small portion of the caul upon the fire.

But it is especially to fire and water that they offer sacrifice. To fire they offer sacrifice by adding dry wood without bark and by placing fat on top of it; and then they pour oil on it and light it below, not blowing with their breath, but fanning it; and those who blow the fire with their breath or put anything dead or filthy upon it are put to death.