The Isolator by Hugo Gernsback, 1925

The image is from the July, 1925 issue of the long defunct magazine "Science and Invention" , which was edited by Hugo Gernsback, who later became famous as a prisoner in the field of science fiction.

The "Isolator" is designed to help focus the mind when reading or writing, not only by eliminating all outside noise, but also by allowing just one line of the next to been seen at a time through a horizontal slit. Obviously, doing away with all distractions in this way could be profoundly counter productive.