Carl Sagan -- he was an astronomer, astrophysicist, cosmologist and great popularizer of science. He was also, it turns out, a lifelong smoker of cannabis. In 1999, and just three years after Sagan's death, Keay Davidson published Carl Sagan: A Life, a biography that made headlines for revealing how Sagan wrote an essay in 1969, using the pseudonym "Mr. X," where he outlined the personal benefits of smoking marijuana. The essay eventually appeared in the 1971 book Reconsidering Marijuana. 35 years old at the time, Sagan explained how the drug heightened his sensory experience, gave him an appreciation for the spiritual realm ("a feeling of communion with my surroundings, both animate and inanimate"), enhanced his enjoyment of sex, and allowed him to achieve some "devastating" insights into scientific, creative and particularly social questions. The drug also gave him a newfound respect for art and music. He wrote:
The cannabis experience has greatly improved my appreciation for art, a subject which I had never much appreciated before. The understanding of the intent of the artist which I can achieve when high sometimes carries over to when I’m down. This is one of many human frontiers which cannabis has helped me traverse.... A very similar improvement in my appreciation of music has occurred with cannabis. For the first time I have been able to hear the separate parts of a three-part harmony and the richness of the counterpoint. I have since discovered that professional musicians can quite easily keep many separate parts going simultaneously in their heads, but this was the first time for me.
You can read the complete essay here.
A quick footnote: later in life, Sagan advocated legalizing medical marijuana, as you can hear below. And his wife, Ann Druyan, who made substantial contributions to the PBS documentary series Cosmos, has since pushed for the outright legalization of cannabis. She served on the Board of Directors of the National Organization for the Reform of Marijuana Laws for a decade.