On the Apparent Magnitude of the Sun when Low and High

...the thinness of a mite, or a spider's web is reached? Therefore, such are the little membranes original: "membranulae," referring to the thin films of atoms that Epicurean philosophers believed fly off objects to create the sensation of sight which they say flow continuously from the surfaces, or the outermost parts of things. And do you wish to conceive of a continuous and long-lasting outflow without any noticeable decrease in the surface?

Think first of a lit candle, whose "finger" a finger's length or thickness of wax is consumed by the heat of the wick original: "ellychnium" in the space of one hour. Since this consumption is continuous, no moment in that hour can be discerned so small that a little membrane is not being drawn out from that finger-sized mass. Indeed, how many moments, or imperceptible parts of time, do you think can be distinguished through the passage of an hour? Certainly as many as the imperceptible particles in a twenty-fourth part of the outermost surface of the primum mobile: in the astronomy of the time, this was the outermost sphere of the heavens that moved all the inner spheres, which surely escape all understanding because of their vast number. I mention this beforehand to suggest the degree of thinness those membranes must possess, which nature knows how to secrete by the force of heat from a mass of wax or fat the size of a finger.

I proceed, and suppose not a candle, but some vessel full of oil, whose surface diameter is several fathoms: or "orgyiae," an ancient unit of length based on the span of outstretched arms. Now, let a wick be lit in the middle. Would it not be many days before that surface, or if you prefer, the height of the oil, had decreased by only as much as the thickness of a spider's web? And yet it is certain that there was a continuous decrease in it because of the continuous action of the flame. Since the flame was never interrupted, no moment could be assigned in which it could be said "now the height is not decreasing," when it had decreased just before and would decrease again just after. But if we were already marvelling at the multitude and thinness of the membranes which come from a finger-sized candle in an hour...

Vocabulary: little membrane, candle, wick, the outermost celestial sphere, oil, spider's web, fathom, decrease.