Violet rays are a good example of a technology that has been proven bunkum but still exists in quack circles.  All a violet ray or violet wand is doing, is passing electricity through your body. There's a seed of truth to it's usefulness for certain muscle disorders, since muscles are basically operating by electrical pulses sent through your body, but when it comes to the many miracle 'healing powers' quack medical practitioners ascribe to them, they've been pretty thoroughly debunked.