There's a honey found in Turkey's Black Sea region, called Deli bal, that contains a natural neurotoxin from rhododendron nectar that can trigger hallucinations and, in higher doses, nausea, seizure, and even death. Over at Modern Farmer, Emma Bryce looks at the "The Strange History of 'Mad Honey':"
…In 67 B.C. Roman soldiers invaded the Black Sea region under General Pompey's command, and those loyal to the reigning King Mithridates secretly lined the Romans' path with enticing chunks of mad honeycomb. The unwitting army ate these with gusto, as the story goes. Driven into an intoxicated stupor by the hallucinogenic honey, many of the flailing soldiers became easy prey, and were slain.
This rich history, along with Turkey's 18th Century trading tradition, seems to account for mad honey's persistence in the present day — and the fact that it is purposefully harvested there. And yet, finding it still amounts to something of a treasure hunt.