Attributed in Wash. Post, 30 Nov. 1952. The Post article is quoting an article in Quick Magazine from the summer of 1951. According to a letter by William S. Rubin in the New York Times, 5 Jan. 1969, this is "a trumpery originated in Il Libro Nero published by Giovanni Papini in 1951."
Jack White (2013). “Mystery of Making It: Reveals the Secrets of Marketing Art-How Artist Senkarik Sold the First Piece in 1980 and has Exceeded $7 Million in Sales”, p.16, Lulu Press, Inc