It is entirely feasible to have a self-created (endogenous) DMT trip, as experientially verified by many psychonauts including Terence McKenna. The only prerequisite is that you've tried DMT before--either by smoking it or by drinking the Amazonian ayahuasca brew. After that, all you need is the luck of having a dream in which you ingest DMT. Since DMT is a neurotransmitter already native to your brain, a hallucinogenic dosage
will promptly be synthesized and released to your receptors--evidently via a natural catalytic cycle. The result is a full-fledged DMT trip, not merely a dreamlike re-creation. As Terence explains in his Alien Dreamtime rave:

And one of the things that I learned about DMT, was that, if you ever had it, even just once, then you can have a dream. And in this dream somebody will pull out a little glass pipe, and then it will happen. It will happen just like the real thing. Because theres a button somewhere inside each and every one of us that gives you a look into the other side.

Combine this with advanced lucid dreaming techniques and you'll be well on your way to understanding the syntactical nature of reality.