Chorded keyboard (a writing system for the blind) uses either 6 or 8 tactile 'points' from which all letters and numbers are formed. When Louis Braille invented it, it was produced with a needle holing successively all needed points in a cardboard sheet. In 1892, Frank Haven Hall, superintendent of the Illinois Institute for the Education of the Blind, created the Hall Braille Writer, which was like a typewriter with 6 keys, one for each dot in a braille cell. The Perkins Brailler, first manufactured in 1951, uses a 6-key chord keyboard (plus a spacebar) to produce braille output, and has been
Polka-dot paint Polka-dot paint Polka dot paint is a paint which produces a polka dot pattern. The paint is traditionally an impossible object, and the subject of a fool's errand prank played upon apprentices in the decoration or construction trade, who are sent to obtain a bucket of polka-dot paint. A polka-dot paint effect has been produced in stage magic, and in the 1950s a polychromatic paint was invented which produced a dotted effect when dry. In the United States several magicians invented a trick in which they demonstrating painting with polka-dot paint. Prior to the performance, an object is pre-painted in