Bundahishn
Seven chieftains of the planets have come unto the seven chieftains of the constellations, as the planet Mercury (Tir) unto Tistar, the planet Mars (Vâhrâm) unto Haptôk-ring, the planet Jupiter (Aûharmazd) unto Vanand, the planet Venus (Anâhid) unto Satavês, the planet Saturn (Kêvân) unto the great one of the middle of the sky, Gôkihar and the thievish (dûggun) Mûspar, provided with tails, unto the sun and moon and stars.
The sun has attached Mûspar to its own radiance by mutual agreement, so that he may be less able to do harm (vinâs).
Of Mount Albûrz it is declared, that around the world and Mount Têrak, which is the middle of the world, the revolution of the sun is like a moat around the world; it turns back in a circuit owing to the enclosure (var) of Mount Albûrz around Têrak.
As it is said that it is the Têrak of Alburz from behind which my sun and moon and stars return again.
For there are a hundred and eighty apertures (rôgin) in the east, and a hundred and eighty in the west, through Albûrz; and the sun, every day, comes in through an aperture, and goes out through an aperture; and the whole connection and motion of the moon and constellations and planets is with it: every day it always illumines (or warms) three regions (kêshvar) and a half, as is evident to the eyesight.
And twice in every year the day and night are equal, for on the original attack, when it (the sun) went forth from its first degree (khûrdak), the day and night were equal, it was the season of spring; when it arrives at the first degree of Kalakang (Cancer) the time of day is greatest, it is the beginning of summer; when it arrives at the sign (khurdak) Tarâgûk (Libra) the day and night are equal, it is the beginning of autumn; when it arrives at the sign Vahik (Capricorn) the night is a maximum, it is the beginning of winter; and when it arrives at Varak (Aries) the night and day have again become equal, as when it I went forth from Varak.
So that when it comes back to Varak, in three hundred and sixty days and the five Gâtha days, it goes in and comes out through one and the same aperture; the aperture is not mentioned, for if it had been mentioned the demons would have known the secret, and been able to introduce disaster.
From there where the sun comes on on the longest day to where it comes on on the shortest day is the east region Savah; from there where it comes on on the shortest day to where it goes off on the shortest day is the direction of the south regions Fradadafsh and Vidadafsh; from there where it goes in on the shortest day to where it goes in on the longest day is the west region Arzah; from there where it comes in on the longest day to there where it goes in on the longest day are the north regions Vôrûbarst and Vôrugarst.
When the sun comes on, it illumines (or warms) the regions of Savah, Fradadafsh, Vidadafsh, and half of Khvaniras; when it goes in on the dark side, it illumines the regions of Arzah, Vôrûbarst, Vôrugarst, and one half of Khvaniras; when it is day here it is night there.