Plutarch, De defectu oraculorum
Goodwin, Ed.

This is the reason why the ancients were used to express numbering or reckoning by πεμπάσασθαι, to count by fives. And I am of opinion that that word πάντα, all, is derived from πέντε, which is to say five, five being compounded of the first numbers. For all the other numbers being afterwards multiplied by others, they produce numbers different from themselves; whereas five, being multiplied by an even number, produceth a perfect ten, and multiplied by an odd number, representeth itself again; not to insist that it is composed of the two first tetragons or quadrate numbers (unity and four), and that, being the first number whose square is equivalent to the two squares before it, it composeth the fairest of right angled triangles, and is the first number which containeth the sesquilateral proportion. Perhaps all these reasons are not very pertinent to the discourse of the present dispute, it being better to allege that in this number there is a natural virtue of dividing, and that nature divideth many things by this number. For in ourselves she has placed five senses, and five parts of the soul, the vital, the sensitive, the concupiscible, [p. 45] the irascible, and the rational; and as many fingers on each hand; and the most fruitful seed disperseth itself but into five, for we read nowhere of a woman that brought forth more than five at a birth. And the Egyptians also tell us that the Goddess Rhea was delivered of five Gods, giving us to understand in covert terms that of the same matter were procreated five worlds. And in the universe, the earth is divided into five zones, the heaven into five circles,—two arctics, two tropics, and one equinoctial in the midst. There are five revolutions of planets or wandering stars, inasmuch as the Sun, Venus, and Mercury make but one and the same revolution. And the construction of the world consists of an harmonical measure; even as our musical chords consist of the posture of five tetrachords, ranged orderly one after another, that is to say, those called ὑπάτων, μέσων, συνημμένων, διεζευγμένων, and ὑπερβολαίων.¹ The intervals also which are used in singing are five, diesis, semitone, tone, the tone and a half, and the double tone; so that Nature seems to delight more in making all things according to the number five, than she does in producing them in a spherical form, as Aristotle writeth.