Dangerous pseudo-science and quackery, produced by Bridge Publications, 4 years after Hubbtard died. It's mainly a compilation of guff he wrote in the 1960s.
They get around medical regulation by saying it's for "spiritual purposes". I've been to the London Purif; staff there imply that is safe and recommended by medical professionals. It isn't. Speak to your doctor first, if you have to see these guys.
Purif is DANGEROUS as it calls for saunas and vitamins far in excess of safe levels. People have suffered from deydration and electrolyte disturbances.
Spending hours and hours in a sauna is not just a bad idea, it could be fatal.
Beware of all the starry-eyed reviews, obviously written by Scientologists, who uncritically regard Hubbard as the greatest, most intelligent man to have ever lived. My jaw dropped at the person who said that his/her IQ went up after doing this. My face is thoroughly embedded in my palm.