Quote by Samuel Butler
When the water of a place is bad it is safest to drink none that has not been filtered through either the berry of a grape, or else a tub of malt. These are the most reliable filters yet invented.
Summary
This quote suggests that when the water quality of a certain location is poor, it is best to avoid consuming it unless it has been filtered through either grapes or malt. Grapes and malt are proposed as reliable filters for purifying water. The quote implies that these natural substances have the ability to improve the quality and safety of drinking water, thus making them preferable filtration options over other methods.