I experimented on myself plenty back in the day. Lots of my experiments had to do with pain - refusing pain medication when it was available to me, prodding places that pained, using more medication than helpful and so on. I remember one instance when I found myself in immence pain and some words came to mind from a Wikipedia article on a Buddhist mantra I had heard long ago. I read that the prescription for this branch of Buddhism was the mere repetition of the line: I take refuge in Amida Budda. Later, I found that the mantra is longer but it was an amazing altered state to find tranquility in that unlike any other purposeful altered state I had experimented with to cope with the pain (e.g. mindfulness, gratitude, imagery....)