For whenever bodies fall through water and thin air, they must quicken their descents in proportion to their weights, because the body of water and subtle nature of air cannot retard everything in equal degree, but more readily give way [when] overpowered by the heavier.
In: Great Books of the Western World (Volume 12), Lucretius: on the Nature of Things, Book Two, l. 230-234 (p. 18)