He invented the double horizontal sundial, now named Oughtred-type after him.[29] A short description The description and use of the double Horizontall Dyall (16 pages) was added to a 1653 edition (in English translation) of the pioneer book on recreational mathematics, Récréations Mathématiques (1624) by Hendrik van Etten and Jean Leurechon. That translation itself is no longer attributed to Oughtred, but (probably) to Francis Malthus.[