William Horatio Bates, Perfect Sight Without Glasses… (1920)
“ The relief in many cases was so striking that I investigated some thousands of cases and found it to be a fact that persons with perfect sight, or the memory of perfect sight - that is, of something perfectly seen - do not suffer pain in any part of the body, while by a strain or effort to see I have produced pain in various parts of the body.By perfect sight is not meant, necessarily, the perfect visual perception of words, letters, or objects, of a more or less complicated form. To see perfectly the color alone is sufficient, and the easiest color to see perfectly is black. ”
