Plutarch, De Iside et Osiride
Goodwin, Ed.

It is fabled by the Egyptians that Osiris's death happened upon the seventeenth day of the month, at which time it is evident that the moon is at the fullest. For which reason the Pythagoreans call that day Antiphraxis (or disjunction) and utterly abominate the very number. For the middle number seventeen, falling in betwixt the square number sixteen and the oblong parallelogram eighteen (which are the only plane numbers that have their peripheries equal with their areas), disjoins and separates them from each other; and being divided into unequal portions, it makes the sesquioctave proportion (9:8). Moreover, there are some that affirm Osiris to have lived eight and twenty years; and others again, that he only reigned so long, for that is the just number of the moon's degrees of light and of the days wherein she performs her circuit. And after they have cleft the tree, at the solemnity they call Osiris's Burial, they next form it into an ark in fashion like a crescent, because the moon, when it joins the sun, becomes first of that figure and [p. 103] then vanishes away. Likewise the division of Osiris into fourteen parts sets forth unto us symbolically the number of days in which that luminary is decreasing, from the full to the change. Moreover, the day upon which she first appears, after she hath now escaped the solar rays and passed by the sun, they term ‘imperfect good;’ for Osiris is beneficent, and as this name hath many other significations, so what they call ‘effectuating and beneficent force’ is none of the least. Hermaeus also tells us, that his other name of Omphis, when interpreted, denotes a benefactor.