How to Test Water Quality, c. 15 BC

Springs should be tried and tested like this: if they flow freely in the open, one should take a good look at the physiques of the people who live in their vicinity before one starts to take water from them: if the locals have robust bodies, fresh complexions, sound legs and eyes without inflammation, then the springs will have passed the test with flying colours.

Vitruvius, On Architecture (trans. Richard Schofield)

When the locals tell you to stop ogling their limbs, tell them you’re just testing the water.