[Considering... tobacco wasn't really a thing until the middle ages, and intimate plant knowledge probably wasn't included in the laundry list of things Rider gained knowledge about when I summoned him, right? Hopefully...]

... A plant. Probably from the nightshade family.

[Taking a pen and a scrap of paper out from an inside coat pocket and scribbling a few precise sketches. Waver's no artist, but you do need some degree of drawing accuracy to correctly draw runes and pentagrams and scientific diagrams, so.]

It'd look something like-- one of these...