Benham's disk, also known as Benham's wheel and Benham's top, is a disk marked with a black and white pattern, which, when spun around, causes people to see colors. It was invented in 1894 by the toy-maker C. E. Benham and originally sold through Messrs. Newton and Co. as the "Artificial Spectrum Top." It is one of a number of spinning disk color illusions first described by Gustav Fechner in 1838. For this reason, the illusory colors are known as Fechner colors. From the beginning, it was realized that the root of the illusion probably lay in the variation of retinal response time with wavelength.