Stanislav Grof (who supervised roughly 4500 LSD sessions and himself took LSD over 100 times) on 5-MeO-DMT:

"We have an amazing book by Ralph Metzner called The Toad and the Jaguar. Ralph traveled all over Europe and in the United States, visiting these groups that were using it, using some illegal loopholes or doing a kind of underground research and he wrote this book where he collected that information in a way that could become the basis of scientific research.

"Now, what is fantastic there is that this substance creates a very short, within an hour, which is within the time of one psychoanalytic session, you can experience significant transformation, even spiritual opening. The substance is methoxy-DMT.

"I have in my book When the Impossible Happens a chapter which is called "The Secret of the Toad of Light" -- there are churches in the American Southwest that are actually using it as a sacrament, called the Church of the Toad of Light.

"I took a fairly large dose, one that is more than is usually used. My first time I really didn't know the dosing. It was estimated 25 milligrams. Today you would use 5 or 10. This was by far the most powerful psychedelic experience I've ever had.

"Within seconds it took me out of my body. There was nothing biographical, no birth experiences, nothing archetypal. I was just facing this incredible source of light, for the lack of a better description. It was beyond anything I could imagine in terms of the brilliancy and incandescence that it had, but also a sense that there was incredible intelligence, creative intelligence going beyond any dichotomies. I couldn't say if it was daemonic or divine. It was just off the scales that I had.

"Coming down from that experience, I had the feeling I was dying -- not from life in to dying but from a place beyond death into a dying body, and after a while it became clear that this was not really dying, it was an experience of dying, and for quite a while I was in a situation where I was an absolutely blissful state and I was having visions of streams of my past life experiences where I had the feeling of dying and being killed in different situations. My body was acting out the agony. It was shaking, twitching, but psychologically, emotionally I was in absolute bliss.

"Then coming down for a week I was in a state in which I would like to live. We were at the time living at Esalen. We had a deck overlooking the ocean. This was the time I was handwriting my manuscripts and giving it to a secretary and having to edit it. In that week I had to do editing of my manuscript, which I could do perfectly lying in the sun there, and I would take a little break and within seconds I had the feeling of oneness with the whole environment, oneness with the world. Then I would open my eyes and I could continue editing.

"But then of course, the consciousness of the industrial civilization came back to do workshops, travel, so I didn't stay in that state but my meditations became much, much deeper and it was not difficult to get into some version of that state just through meditation.

"So I think this would be an amazing substance to try for practical reasons. Because you will not find psychiatrists like my self, in the 60's and so on, sitting for six hours with their patients but they could certainly do a one hour session with the methoxy-DMT and I think signifcant therapy could be done within this very short time.

"It's also, according to Ralph Metzner's observations, it's a substance where the experience ends very cleanly. There's no lingering on. So there is a very powerful experience but also a good closure.

"So this is my experience with methoxy-DMT. Now it's very very popular. For example, we had the Tranpsersonal Conference in Prague and there were lectures about it and of course there were people who had access to the toad material, to the excretions or secretions of the glands. So it's becoming a very popular substance right now."[1]

[1] - From about 38 minutes in to Tim Ferris' interview with Grof here: https://www.youtube.com/watch?v=3mdYUmvTeig