I'm reading The Little Book of Cannabis: How Marijuana Can Improve Your Life by Amanda Siebert, and I came across this passage in Chapter 3:
"Even William Shakespeare, one of the world's greatest dramatists, is thought to have used cannabis. This is the conclusion South African scientists came to in 2001 when they discovered traces of cannabis in clay tobacco pipes at Shakespeare's residence in Stratford-upon-Avon. While it's certainly a controversial point that most academics will contend with, not least because of Shakespeare's love of word play, the Bard does mention 'a noted weed' in Sonnet 76. Some believe he is referring to cannabis."
There are articles about this, including this one. Interesting, but I'm not totally convinced yet. Kind of a big maybe.