Heronis Alexandrini spiritalium liber

the particles of sand is similar to the vacuums contained within the air. For this reason, with a certain force approaching, it happens that the air is condensed and settles into the places of the vacuums, with the bodies being compressed together against their nature. But when the release is made, it is restored again to the same order because of the natural tension of the bodies, just as in the clippings of horns and in dry sponges, which, if they are compressed and released, return again to the same place and take on the same bulk. Similarly, if by some force the particles of air have been pulled apart from one another, and a larger empty place is made than is natural, they return to themselves again. For through a vacuum, it happens that a rapid movement of bodies occurs, with nothing resisting or pushing back, until the bodies apply themselves to one another. If anyone, therefore, taking a very light vessel with a narrow mouth, and applying it to the mouth, has sucked out the air and let it go, the vessel will immediately be hung from the lips, with the vacuum attracting the flesh so that the emptied place may be filled. Thus, from these things, it is clear that the place which was in the vessel was entirely vacuum. But this is also clear by another reason. For...