I was engaged in a conversation about at what point in human history were we capable of understanding that eating mushrooms were the cause of hallucinations. What early civilizations identified certain foods as being known hallucinogens?
The use of hallucinogens dates back to prehistory. Psychedelic mushrooms grow naturally in Northern Europe and there's a lot of speculation that in some places they were probably used as a part of shamanistic rituals. The use of peyote, mescaline, and sativa for religious/spiritual purposes in the Americas also begin in prehistory, but have been used for thousands of years.
Herodotus says that the Scythians would hotbox tents with "hemp seeds" and a dish of coals.
Sorry if this isn't up to standard, but I think the general answer to your question is "too far back for us to know."