Mandrake

(mandragora, dudain)
Little problem with this herb. It's been referenced by many sources for thousands of years, including the Bible (Genesis, chapter 30). It's well known in legend and lore. (As an example, people thought it screamed when it was pulled out of the ground. Dogs were used to pull the roots up, so that no humans would die from the sound.) But noone really knows which plant they were referring to.
Oh, sure, we know it was man-shaped, sort of like a double carrot. We also know it was used as an aphrodisiac and was probably a hallucinogenic narcotic. But what plant was it?
Modern claims to the identity include jimsonweed, English white briony, truffles (yeah, right), and May apple, which was once actually called "mandrake". The plant most commonly referred to as mandrake is Mandragora officinarum, a Mediterranean relative of the potato. May apple (Podophyllum peltatum), a plant found in the American Northeast, runs a close second. However, both are potentially toxic and should probably be avoided.
Ginseng, which has the correct shape and is sometimes sold under the name "man root", is a better option.