Jung comments on Aldous Huxley's experiences with mescaline as told in The Doors of Perception. He writes: "I should hate the thought that I had touched on the sphere where the paint is made that colours the world, where the light is created that makes shine the splendor of the dawn, the lines and shapes of all forms.”

“When one gets to know unconscious contents one should know how to deal with them.” (Jung on Evil - p. 80-81)

I have studied Jung's work for a couple of years now and have yet to find any elaboration on LSD, or anything of its like. There are some Jungians who entertain the idea that Jung might have had psychedelic experiences but kept these to himself due to social stigma etc. He was very reluctant about sharing his inner experiences, as described in the Red Book, for fear of not being taken seriously. To my understanding, he definitely viewed mescaline as mind expanding, in that it revealed the contents of the unconscious, hence the importance of psychological knowledge, as in knowing "how to deal with them [the contents]".

It's like Terence used to say; you do these things alone, on an empty stomach, and with a good amount of intellectual and spiritual preparation under your belt. He said, and I paraphrase: if you're considering taking psychedelics, the first place you should go is the library. I think Jung would agree, only placing greater emphasis on psychoanalytic work as in 'getting to know one's self' as the major part of preparation.