Rebecca pointed me at this article from NPR in which art historian David Bellingham posits that the Botticelli painting "Venus and Mars" depicts Mars in a state of intoxication from ingesting Datura, also known as Jimsonweed shown in the borders of the painting. Datura is a hallucinogenic and poisonous relative of Belladonna, also known as Deadly Nightshade. This sounds plausible, if in fact Datura use was known in Europe at the time of the painting. What sounds way less plausible to me is when Bellingham says that art historians overlooked the Datura in the painting because they thought that Botticelli was "probably just making a pretty frame to the painting."
I don't think any art historians thought that. Especially not about Botticelli or other artists of his time. Any art historian familiar with the period would know that any object, flora, fauna, person, deity, could be and are often used as symbols, puns, inside references, jokes, tributes, etc. The meanings of these various things might not be known exactly, but they are assumed to have been used for subtle or not so subtle symbolic purposes. In Art in Renaissance Italy an example is given of Botticelli's "Primavera" in which the figure of Venus is haloed by a laurel bush in the back
ground. This is thought by the authors to represent not just a "pretty frame" but to be a homophonic reference to Lorenzo di Medici of Florence, Botticelli's patron and financial backer. In Marjorie Stokstad's Art History the orange trees in this same painting are pointed out as a symbol of some kind representing the Medici clan. It's not fair to say that art historians somehow 'missed' the jimsonweed hanging out in this painting. I think it's more likely that this interpretation was passed over because it's not known if datura use was even present at the time and place when this painting was completed. It's definitely provocative, though. Mars certainly looks like he's stoned, but I think more research would be needed to really say for certain.