Back in 1832, an American physician named Charles Knowlton suggested douching as a form of birth control. He advised that, after intercourse, women inject a syringe full of a water-based solution that included (but wasn’t limited to) salt, vinegar, liquid chloride, zinc sulfite, and aluminum potassium sulfite into their vagina. But as douching and other early birth control methods became more popular, the country saw some moral pushback. In 1873, as part of the “social purity movement,” Congress passed the Comstock Law, making it illegal to use the U.S. Postal Service to disseminate any information or paraphernalia regarding “erotica, contraceptives, abortifacients, or sex toys.”