See this letter from the Lubavitcher Rebbe regarding LSD:
http://www.chabad.org/library/article_cdo/aid/848022/jewish/Can-Hallucinogenics-Aid-Spirituality.htm
He argues that one may only take drugs that are necessary for one's health, and that it is better to seek spiritual stimulation through learning chassidus.
I would add that since there are real health dangers (especially to mental health but also physical health), one should not take such drugs. You say there are no harmful side effects but that simply isn't true -- many people suffer from panic attacks or hallucinogen persisting perception disorder (HPPD) after taking drugs like peyote.