The "tripping" scene from "Easy Rider" comes to mind — same era though (NSFW, isn't Tony Basil in this scene? https://youtu.be/W2x20CV0EbI).

Also, this clip (NSFW) from "Altered States" is just as trippy: https://youtu.be/E1ZGEvJPQ6A

The complete Roger Corman film "The Trip" (1967) referenced in the article is on YT in the U.S.: https://youtu.be/FmZCwcGu_2I