Plutarch, De Iside et Osiride
Goodwin, Ed.

Moreover, in the sacred hymns of Osiris they call him up ‘who lies hidden in the arms of the sun.’ And upon the thirtieth day of the month Epiphi they keep a certain festival called the Birthday of the eyes of Horus, when the sun and the moon are in one direct line; as esteeming not only the moon but also the sun to be the eye and light of Horus. Likewise the three and twentieth day of the month Phaophi they make to be the nativity of the staves of the sun, which they observe after the autumnal equinox, intimating hereby that he now wants, as it were, a prop and a stay, as suffering a great diminution both of heat and light by his declining and moving obliquely from us. Besides this, they lead the sacred cow seven times about her temple at the time of the winter solstice. And this going round is called the seeking of Osiris, the Goddess being in great distress for water in winter time. And the reason of her going round so many times is because the sun finishes his passage from the winter to the summer tropic in the seventh month. It is reported also that Horus, the son of Isis, was the first that ever sacrificed to the sun upon the fourth day of the month, as we find it written in a book called the Birthdays of Horus. Moreover, they offer incense to the sun three times every day; resin at his rising, myrrh when it is in the mid-heaven, and that they call Kyphi about the time of his setting. (What each of these means, I shall after wards explain.) Now they are of opinion that the sun is atoned and pacified by all these.

[p. 113] But to what purpose should I heap together many things of this nature? For there are some that scruple not to say plainly that Osiris is the sun, and that he is called Sirius by the Greeks, although the Egyptians, adding the article to his name, have obscured and brought its sense into question. They also declare Isis to be no other than the moon, and say that such statues of her as are horned were made in imitation of the crescent; and that the black habit in which she so passionately pursues the sun, sets forth her disappearings and eclipses. For which reason they used to invoke the moon in love-concerns; and Eudoxus also saith that Isis presides over love-matters. Now these things have in them a show and semblance of reason; whereas they that would make Typhon to be the sun deserve not to be heard.