Psalmanazar’s invented Formosan alphabet, which was still included in books of languages well into the 18th century: featured in a 1705 edition of George Psalmanazar's An Historical and Geographical Description of Formosa.
Featured on PDR in the essay Made in Taiwan? How a Frenchman Fooled 18th-Century London
Benjamin Breen on the remarkable story of George Psalmanazar, the mysterious Frenchman who successfully posed as a native of Formosa (now modern Taiwan) and gave birth to a meticulously fabricated culture with bizarre customs, exotic fashions, and its own invented language.