The only way to truly hallucinate or "trip" without the probable chance of organ damage is to consume tryptamine-based hallucinogens (LSD, psilocybin mushrooms, DMT). Oxygen deprivation, sleep deprivation, and dehydration all carry heavy risks, while tryptamines have been shown to cause negligible, if any, brain or organ damage when used responsibly (i.e., not taking 10 hits of acid every weekend). The biggest danger with tryptamines is the psychological stress the experience can inflict on the user, so one should only take them if they are in a comfortable setting with trustworthy company. Never underestimate a psychedelic drug. Trust me on that.