Charles Knowlton didn't think much of the laws of Massachusetts, at least when they interfered with his medical practice. By the time he opened a practice in the town of Ashfield, he had already been arrested in Amherst, MA for selling "infidel" books and had spent two months in the Worcester County Jail for grave robbery.
So it's unlikely that he considered what his neighbours would think when he wrote The Fruits of Philosophy in 1832, a blisteringly-frank treatise on family planning. He undoubtedly had his patients in mind: his secularist beliefs didn't sit well with the affluent Congregationalists in town, so his patients came primarily from his poorest neighbours. Knowlton saw how they suffered, and thought their lives could be better if they had fewer children.
In how many instances does the hard-working father, and more especially the mother, of a poor family remain slave throughout their lives, tugging at the oar of incessant labour, toiling to live, and living to toil; when, if their offspring had been limited to two or three only, they might have enjoyed comfort and comparative affluence? How often is the health of the mother, giving birth every year to an infant — happy if it be not twins — and compelled to toil on, even at those times when nature imperiously calls for some relief from daily drudgery, — how often is the mother's comfort, health, nay, even her life, thus sacrificed?
In four short chapters, Fruits describes male and female sexual anatomy, explains how children are conceived, and offers some (rather frightening) advice for treating impotence.
To stimulate the genital organs more directly, cayenne, Dewees' tincture of guaiac, or tincture of flies, may be taken. I have given directions for making and taking the tincture of flies, chiefly because it is esteemed one of the best remedies for impotency caused by or connected with nocturnal emissions, to which I have before alluded.
The book also contains contraceptive advice, recommending both condoms and a sort of vaginal sponge paired with a do-not-try-this-at-home spermicidal douche.
Another check which the old idea of conception has led some to recommend with considerable confidence, consists in introducing into the vagina, previous to connection, a very delicate piece of sponge, moistened with water, to be immediately afterward withdrawn by means of a very narrow ribbon attached to it … well moistened with some liquid which acted chemically upon the semen, it would be pretty likely to destroy the fecundating property of what might remain…syringing the vagina immediately after connection with a solution of sulphate of zinc, of alum, pearl-ash, or any salt that acts chemically on the semen, and at the same time produces no unfavorable effect on the female.
Knowlton started quietly lending his book out to his patients. Word got out. Within a year the town's minister launched a campaign against "infidelity and licentiousness," which soon saw Knowlton tried, convicted, and sentenced to three months hard labour in Cambridge, MA. The book was reprinted again and again through the 1890s.