This weekend, New York City’s American Museum of Natural History opens its latest exhibit, The Power of Poison. There, visitors will get up close and personal to poisonous creatures, visit a forensic lab to work through real-life poison cases, and see how poison can actually be used for good. We went to a preview of the exhibit; here are just a few things we learned.

1. There’s a reason we say “mad as a hatter”: In the 1800s, many hatters were poisoned by mercuric nitrate used to remove fur from animal skins; it made them behave irrationally and caused tremors, among other terrible effects. The use of mercury in hat making wasn’t banned by the U.S. government until 1941.

A beaver felt top hat. ©AMNH/C. Chesek

2. Another name for those afflicted by the mad hatter syndrome: The Danbury Shakes, named for Danbury, Connecticut, which for most of the 19th century was known as the “hatting capital of the world.”

3. As caterpillars, longwing butterflies feed on the poisonous passionflower, metabolizing the plant’s compounds before they can combine to create cyanide. The butterflies retain the poison, and their brightly colored wings let predators know that they’re toxic.

A flame butterfly caterpillar. ©AMNH/R. Mickens

4. Kalam speakers in Papua New Guinea have a name for the poisonous pitohui that means “bird whose bitter skin puckers the mouth.”

5. Howler Monkeys, which eat diets full of plant toxins, also munch on clay—which scientists suspect they eat to counteract the effects of the toxins.

6. It’s impossible to make yourself immune to substances like mercury, lead, and cyanide by taking small doses. Instead, they build up in the body and eventually cause death.

7. The Snow White fairytale—in which a witch takes a bite of an apple that, when Snow eats it, puts her into a deathlike state—isn’t that far fetched: There are poisons that make people appear dead, including pufferfish toxins and some snake venom, which interfere with the nerves that make muscles move. (But if Snow’s lung muscles were paralyzed, there would be no revival for her.) Sharing poisonous food happens in real life, too; one Malaysian trick involved putting poison on one side of a knife before cutting the food, ensuring that only one side would be toxic.

8. Mercury was used in a lot of medications, including children’s teething powder as recently as 1948. Even people like Abraham Lincoln and author Louisa May Alcott took medicines containing mercury.

©AMNH/C. Chesek

9. There were a number of objects people believed would protect them against poison, including amethysts, opals, and emeralds. Another was “dragon tongues”—or fossilized shark teeth—which Europeans living centuries ago wore as charms, dipping them into food to purify it of poison.

10. Not all poisons are bad! A compound in gila monster venom was found to lower blood sugar and is being used in a treatment for Type II diabetes, while scientists are exploring using the venom of the Chilean rose tarantula to treat muscular dystrophy.