Heronis Alexandrini spiritalium liber

For let a sphere be constructed having the thickness of a plate, so that it may not easily be broken, containing about eight cotylae a liquid measure of about half a pint, and closed on all sides. It is necessary, therefore, to pierce it and to lower a bronze siphon, that is, a slender tube, not touching the place that is opposite the pierced point along the diameter, so that the water can flow; but another part of it should protrude outside the sphere by about three fingers, and it is necessary to block the circumference of the hole, through which the siphon is lowered, with tin, gripping both the siphon and the external surface of the sphere, so that when we wish to blow through the siphon with our mouth, the spirit referring here to air or breath may in no way escape from the sphere. Therefore, let us look at what happens. For with air existing in it, just as in other vessels which are called empty, and filling the whole place that is in it, and by a certain continuity applied to its circumference, with no place at all being empty as they think, we would be able to neither send in water, nor would other air be able to enter without the previous air that was in it departing; and if