[alx]

"The Shulgin Rating Scale is a simple scale for reporting the subjective effect of psychoactive substances at a given dosage, and at a given time. The system was developed for research purposes by the American biochemist Alexander Shulgin and detailed in his book PiHKAL"

https://en.wikipedia.org/wiki/Shulgin_Rating_Scale

PLUS FOUR (++++) [...] If a drug (or technique or process) were ever to be discovered which would consistently produce a plus four experience in all human beings, it is conceivable that it would signal the ultimate evolution, and perhaps the end, of the human experiment.