" In 1775, Cumming patented the S-bend. This became the missing ingredient to create the flushing toilet—and, with it, public sanitation as we know it. Flushing toilets had previously foundered on the problem of smell: the pipe that connects the toilet to the sewer, allowing urine and feces to be flushed away, will also let sewer odors waft back up—unless you can create some kind of airtight seal. "

― Tim Harford , Fifty Inventions That Shaped the Modern Economy