Mechanismus der menschlichen Sprache nebst Beschreibung seiner sprechenden Maschine.

Kempelen built the first successful speech synthesizer that produced not only some speech sounds, but also whole words and short sentences. His final version of the machine, which differs slightly from the version shown in the book, is preserved in the Deutsches Museum Munich, in the department of musical instruments. Digital facsimile from deutschestextarchiv.de at this link. Degen issued an edition of Kempelen's book in French also in 1791. Digital facsimile of the French edition from Google Books at this link.

Parallel English translation and edited German text as Der Mechanismus der menschlichen Sprache. / The Mechanism of Human Speech.: Kommentierte Transliteration & Übertragung ins Englische / Commented Transliteration & Translation into English. Herausgegeben von / Edited by Fabian Brackhane, Richard Sproat & Jürgen Trouvain. 2 vols. Dresden, 2017. Digital facsimile of the modern edition was available at this link: http://www.coli.uni-saarland.de/~trouvain/Kempelen-Web_2017_07_31.pdf