For the first time, an ecstatic aura has been evoked through the electrical stimulation of the dorsal anterior insula during presurgical invasive intracerebral monitoring in a patient who did not suffer from an ecstatic form of epilepsy.
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On the MEQ‐30 questionnaire, completed to describe the ecstatic symptoms experienced during the AI3‐4 stimulations, the patient had a total score of 130 of 150 points... which is considered a "complete" mystical experience.

From the Psychonaut subreddit, What's the most interesting thing to happen to you on a psychedelic? Of course selection bias is going to make psychedelics seem more reliably mind-blowing than they really are. This whole thread is better than my answer, which would be sensing the personalities of trees.

And from Ask Old People, What coincidence has occurred in your life that pretty much convinced you that we are living in the matrix? My explanation for all this stuff is simply that the fundamental unit of reality is the first person perspective. Each of us is dreaming the world on the fly, and we've dreamed up a physical universe as one way to be characters in each others' stories; but it's not seamless and it's not the only way.