A doctor heard from a traveler of a method used by Central American Indian women by which they took a wild yam and pressed it with a particular mushroom between hot rocks, and then ate it. This prevented unwanted childbirth! A while back I did some searching on contraceptive methodology. There were several places that mention wild yams as a contraceptive, but no details on how to use it. The other most common result was Queen Ann's Lace or wild carrot. Used since Babylonian times, it contains a substance that has abortive properties. Apparently the practice was for the young ladies to pick a seed head while returning home the next morning and munch on the seeds. I'm fairly certain that domesticated (edible) carrots retain this substance in their seeds, but could not verify it. The primary differences in QAL and the modern carrot are in taste and root development. In fact, when culturing carrots for seed harvest, one needs to be sure that no QAL is growing within a mile of the crop. I did find information on the use of vinegar and citric acid fruits. There were cautions against the use of these acids related to comfort, especially the citrus fruits, but no apparent proof against their efficacy.
Offered by Roger.
Queen Annes Lace also known as Wild Carrot.
Offered by Liai.
Apparently, the Essenes used rosehips for contraception. Lemon pulp has a similar effect - creating an acidic environment which is inhospitable to the sperm.
Offered by Jennifer.
The Universe in it's wisdom has supplied every continent with plants and herbs to control procreation. The common poplar tree is an excellent menses stimulator. It was not until the "witches" were burnt and the patriarcal societies became dominant that common usage of these herbs fell into disuse and women were encouraged to stay "barefoot and pregnant".
Offered by Regina.
In some parts of India, they use cow dropping as birth control. From what I heard its quite effective.
Offered by Kurt.
EEEWWWW! My guess is that cow droppings would act as a repellent to keep males at a distance! Another more hygienic method of birth control is to soak a piece of sponge in vinegar and place it into the vagina prior to intercourse. A string tied around the sponge is used to pull it out several hours later. The acid creates a hostile environment for the sperm.
Offered by Cas.