Carl Sagan. AP Drugs. Those illegal mind-altering poisons. Can you believe people actually do these things?

Believe it.

And it's not just the laypeople who are using. There are plenty of brilliant heavyweights in the science and technology worlds that have said they enjoy their drugs.

Famous astrophysicist Carl Sagan secretly loved weed, a fact that only came to light after his death. Steve Jobs made several mentions throughout his lifetime about his LSD experiences being incredibly important to him.

In fact, a 2011 Johns Hopkins University study gave test subjects psychoactive doses of magic mushrooms. Of the 51 participants in the experiment, roughly two out of three identified the effects of their mushroom trip as one of the five most meaningful experiences of their lives.

In an interview with Wired, an early Cisco employee named Kevin Herbert said that a drug like LSD can be an effective tool in problem solving. He believed it so strongly that he stepped in to prevent Cisco from ever drug testing a technologist.

So whether it was for furthering the great cause of humanity or to seek an escape from the stresses of the world, here are 11 people who were both brilliant and sometimes on drugs.