“There is more evidence to prove that saltness [of the sea] is due to the admixture of some substance, besides that which we have adduced. Make a vessel of wax and put it in the sea, fastening its mouth in such a way as to prevent any water getting in. Then the water that percolates through the wax sides of the vessel is sweet, the earthy stuff, the admixture of which makes the water salt, being separated off as it were by a filter.”
[This is an example of Aristotle giving proof by experiment, in this case, of desalination by osmosis.]
Even 2,000 years after Aristotle’s rough experiment, scientists, students, and teachers still have something to say about this phenomenon; which “plays a role in the blood circulation, keeping just the right balance between the water content of the blood and the surrounding tissues. Osmosis drives fluid flow in the kidneys, preventing waste products from accumulating to dangerous levels. Osmosis is also the driving force behind plant cell expansion, playing a role in flower and fruit growth.” (Via Scientific American, May 1, 2013).
The following video from Khan Academy illustrates what Aristotle observed. It also provided explanations through the use of experimental models: