One of the earliest use of plant-matter was by burning it, breathing in the smoke. Some plants would help with respiratory problems, some with nausea or head-aches. Some plants would calm and relax, others were considered to open the mind for the unseen – the world of the Gods.
So of course I was not surprised when I stumbled upon this article:
http://www.sciencedaily.com/releases/2008/05/080520110415.htm
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