Sun rays
In 1893 Dr. V.O. Thayer had a paper in the Southern California Practitioner on Solar Therapy. The treatment consists in concentrating the sun’s rays by means of burning glasses on the diseased part until it is slightly burnt or charred. When healed, which soon follows, repeat until cured. He claimed to have cured, by this means, varicose veins, all sorts of ulcers, cancers, removed birth marks, India ink and powder marks, warts, wens and other morbid growths on the skin. Unlike other caustics, it can be applied with perfect safety upon the most delicate tissues. The irritation and inflammation following its application is surprisingly slight and of short duration. Pain subsides immediately. There is a curative power in the rays of the sun yet unexplained.