|Gesner, Nomenclator aquatilium animantium (1560)|
"Thou ought to knowe that clere rennynge Waters that ben nyghe to cytees in pure grounde as small brokes be the best and lyghtest. Water that cometh out of stony erthe where as is moche fumosytees is hevy, contagyous, & noysom. Water of puddles or fenne full of frogges, addres, and other venymous worms be unholsom."
Secretum secretorumA little water-quality issue you may have overlooked: poisonous snakes are not potable.