Three women gather around a cauldron, mixing an odd assortment of ingredients.

Eye of newt and toe of frog. Wool of bat and tongue of dog.

“Double, double toil and trouble,” the “Macbeth” witches chant in one of the best-known scenes by William Shakespeare.

Adding the finger of a birth-strangled babe sounds gruesome, but when it came to the other ingredients, the Bard may not have been too far off.

After all, long before medical degrees and emergency rooms, people — and more specifically, women — were coming up with their own cures for illnesses from the plague to depression.

That’s the focus of “Beyond Home Remedy: Women, Medicine and Science,” the newest exhibit at the Folger Shakespeare Library. The exhibit studies how women created medicines, worked as midwives and treated injuries in the past, tying some examples back to Shakespeare’s plays. Through their treatments, women expanded the scientific knowledge of the time as well.

Making something with the “fillet of a fenny snake,” like those “Macbeth” witches, doesn’t sound appealing, but it was common for women to use snakeskins in various recipes (though the recipe books don’t note why the snakeskin was necessary). Other questionable ingredients include the use of urine to cure blindness (“a special water for sore Eyes if a man have lost his sight 5 years if it be possible it will restore within 40 days”) and mole blood for baldness (“to recover Hair in any part of the body”).

An animal skull sits in the ingredients case, with the description that people used skulls — including human ones — to prevent convulsions and fits. It brings to mind a scene from “Hamlet,” when the title character comes across the skull of poor Yorick. At that point in the play, Hamlet has already acted insane on several occasions. Perhaps this was Shakespeare’s way of telling the audience that Hamlet wasn’t just acting.

Aside from the animal ingredients, different herbs and vegetables were used to treat everything from scurvy (oak leaves) to migraines (mustard seeds).

Ophelia in “Hamlet” knew these uses well. Even in her madness after her father’s murder, she sings about the uses for herbs.

“There’s rosemary, that’s for remembrance,” she sings. “And there is pansies. That’s for thoughts.”

She notes how she would use violets “but they withered all when my father died.” Women used violets to cure melancholy and provide comfort. When the flowers died in the play, it was Shakespeare cleverly adding foreshadowing based on common knowledge of the time period.

Though the violets didn’t help Ophelia, their use continued for centuries. In a featured piece in the exhibit, Martha Washington wrote in her recipe book of a syrup of violets. The mixture of crushed violets, water and sugar had evolved since Shakespeare’s time; by the Revolutionary period, it was used to ease fevers and coughs and to relieve inflammations of the liver, lungs and chest.

While these applications sound bizarre today, they were based on the teachings of women who practiced medicine back then. Doctors were few and far between, especially in rural areas, so women, as natural caretakers, were expected to step in as replacements.

“Medicine was a part of a woman’s education,” said Amy Arden, a Folger Shakespeare Library spokeswoman. “We take for granted things like pharmacies and hospitals, so we forget how much time and effort went into producing one medicine.”

One such remedy was snail water, used to cure consumption and jaundice. Two cases in the exhibit lay out the lengthy process. Women would gather garden snails and wash them in beer before adding ingredients such as earthworms, bark and rosemary to the mix. After leaving the combination to stew overnight, more ingredients such as deer’s horn and cloves were added.

The combination sounds more like a witch’s potion than a modern medicine. But an oath administered to midwives, similar to today’s Hippocratic Oath taken by doctors, warned against the use of witchcraft.

“That you shall not in any wise use or exercise any manner of Witchcraft, Charm or Sorcery, Invocation, or other Prayers then may stand with Gods Laws and the Kings,” the oath reads.

The oath exemplifies the seriousness of the jobs women aimed to do.

“It was the beginning of a true scientific inquiry, but for these women, it was really about providing different types of care,” Arden said. “They did it because they had to.”

“Beyond Home Remedy: Women, Medicine and Science” is a free exhibit that runs through May 14.