Book I: 131-131
The following are certain Persian customs which I can describe from personal knowledge. The erection of statues, temples, and altars is not an accepted practice amongst them, and anyone who does such a thing is considered a fool, because, presumably, the Persian religion is not anthropomorphic like the Greek. Zeus, in their system, is the whole circle of the heavens, and they sacrifice to him from the tops of mountains. They also worship the sun, moon, the earth, fire, water, and winds, which are their only original dieties: it was later that they learned from the Assyrians and Arabians the cult of Uranian Aphrodite. The Assyrian name for Aphrodite is Mylitta, the Arabian Alilat, ther Persian Mitha. As for ceremonial, when they offer sacrifice to the dieties I mentioned, they erect no altar and kindle no fire; the libation, the flute-music, the garlands, the sprinkled meal — all these things they have no use for; but before a ceremony a man sticks a spray of leaves, usually myrtle leaves, into his headress, takes his victim to some purified place and invokes the diety to whom he wishes to sacrifice. The actual worshipper is not permitted to pray for any personal or private blessing, but only for the king and for the general good of the community, of which he is himself a part. When he has cut up the animal and cooked it, he makes a little heap of the softest green-stuff he can find, preferably clover and lays all the meat upon it. This done, a Magus (a member of this caste must be always present at sacrifices) utters an incantation over it in a form of words which is supposed to recount the Birth of the Gods. Then after a short interval the worshipper removes the flesh and does what he pleases with it.
...They have a profound reverence for rivers: they will never pollute a river with urine or spittle, or even wash their hands in one, or allow anyone else to do so... There is another practice, however, concerning the burial of the dead, which is not spoken of openly and is something of a mystery: it is that a male Persian is never buried until the body has been torn by a bird or a dog. I know for certain that the Magi have his custom, for they are quite open about it. The Persians in general, however, cover a body with wax and then bury it. The Magi are a peculiar caste, quite different from the Egyptian priests and indeed from any other sort of person. The Egyptian priests make it an article of religion to kill no living creature except for sacrifice, but the Magi not only kill anything, except dogs and men, with their own hands but make a special point of doing so; ants, snakes, crawling animals, birds — no matter what, they kill them indiscriminately. Well, it is an ancient custom, so let them keep it.