According to Megan Garber, writing for The Atlantic in early October 2013 (click blog title for link), apparently, one of the fungi that feeds in old rye bread (ergot) is somewhat hallucinagenic. It makes people sick when they invest it, but absorption through the skin causes a flying-like sensation. So between the 1300s and the 1700s people used to take that mold, along with brewed up roots and other things (witches brew) and rub it on a broom handle. Then ladies would insert that between their legs (no panties back then) and get hi. This is why witches "fly" on brooms.
But sometimes people got high from unwittingly eating the mold. Or bein forced to tear it cause nothing else was around:
"The Massachusetts of 1692 likely did see an outbreak of the fungus that had contributed, in other contexts, to 'witch's brew.'
The epicenter of the outbreak? Salem."