Marijuana is a 'recreational' drug.
(..) MARTY: Hi, Einie. Hi, buddy. DOC: What's this? MARTY: A souvenir. years of sports statistics. DOC: Hardly recreational reading material. Doc, what's the harm in bringing back some info on the future? We could place some bets. DOC: I didn't invent the time machine for financial gain! (..)1989 Back to the Future Part II