Well, It's humanly impossible to O.D. on salvorin a (active chemical in salvia divinorum) but roughly a gram. I myself made a a nice cup of salvia tea just last night by simply removing the contents of a teabag, and adding about a gram or so of salvia. 45 minutes to an hour later I was rolling around on the floor in my trip... but be warned the effects of the tea can last up to several hours.