EDITORS' DISCLAIMER: Cracked does not endorse eating the below foodstuffs for the express purpose of getting high, as the side effects are usually horrible enough to make you forget you were high in the first place. Thus the information in this article should only be used for scintillating chitchat at cocktail parties and around the office.
Rye grain is occasionally infected with the ergot fungus. Ergot contains several psychoactive chemicals such as ergotamine, a compound used in the synthesis of LSD. So if some day your half-eaten sandwich suddenly sprouts a mouth and prophesizes doom for the human race, you'll know why.
Ergot outbreaks are rare so eating a Reuben will most likely not turn you into Hunter S. Thompson at the Kentucky Derby. In the off chance that you're a crazed miller who really, really wants to get high on tainted grain, be forewarned that an ergot infection is roughly one part psychosis, two parts gangrenous sores.
But most modern farmers clean their rye in a potassium chloride solution to guard against, something medieval farmers never did. Thus, the inbred masses of yore lived unaware that their daily bread contained "holy fire," ye olde term for ergotism. And since entire villages often got their bread from the same miller, an outbreak could lead to an entire town full of hallucinating people, completely unaware that they and everyone around them was on the equivalent of bad acid (And if you think this sounds hilarious, stick around for the fun fact about the time it happened to a Puritan town in Massachusetts). Between the "holy fire" and your ancestors' tendency to binge drink in the absence of potable water, it's a miracle we got out of the Dark Ages.
Modern historians blame ergotism for a slew of old-timey panics and superstitions, ranging from werewolves to the Salem Witch Trials. British author John Grigsby even speculates that the legend of Beowulf came from stoned Vikings who "inhaled the holy fire."