There is a good book I recommend called DMT:The Spirit Molecule by Dr. Rick Strassman.
As far as I know he's the only MD to get clearance for experiments with this drug in a controlled setting.
Huxley, Leary, et al have documented the effects of psychedelics like LSD and mescaline;
but prior to Strassman, there hasn't been anything on the short-acting(yet far more intense) tryptamines.
He administered pure DMT via intravenous route, to many patients over the course of a few years, and documented their experiences.
All the patients chosen were somewhat experienced with more widely known psychedelics. This was done to lower the risk of them having a "bad trip".
Despite their familiarity with psychedelics, all the patients were shocked at how vivid and real the experience felt. Unlike drugs like LSD,
DMT really does take you to another world. There is no overlay of visuals upon the "real". It is far more powerful than that.
The real dissapears.
By the end of the book you see that the patients are left asking some powerful questions about their experiences.
It is spiritual for them. They believe that the beings and places they find during the trip are not products of their brain, but real existing entities and worlds.
If you think of the brain as a filter(as Huxley did), cutting out portions of reality not pertaining to you as a biological being,
then it seems possible that this is true. There could be portions of reality that we filter out because they provide superfluous information about entities and places we don't need to know about.