The physionotrace is an early pre-photographic intaglio printing method and an example of one of the methods used to mechanically transpose an image, in this case a portrait, to a printing plate.
While the silhouette was at its zenith, a still better process for executing mechanically and rapidly small and cheap portraits was introduced in France, the physionotrace. The instrument was a wooden framework about 1 meter high, containing a vertical pantograph and a reticulated "sight" to keep the operator’s eye always in the same position relative to the sitter, who was posed file behind the apparatus. When the artist moved the pointer over the outlines of the face, the pencil at the other end of the pantograph drew these outlines on paper in nearly natural size. By a second pantograph operation the portrait was reduced to 5-7 cm. in diameter, and was then engraved in the usual way. Gilles-Louis Chretien (1754-1811), a violoncellist in the royal orchestra at Versailles, exhibited his physionotrace machine to the Academie des Sciences in 1786. The novelty lay in its application to small portraits, and their multiplication by subsequent engraving, rather than in the instrument itself. Chretien’s partner Edme Quenedey (1756-1830), a professional artist, opened a physionotrace studio at the Palais Royal in June or July 1788. He made the original drawings and the reductions, which were engraved by Chretien at Versailles. The original sketch, costing 6 livres (= francs) could be made in four minutes, and for another 15 livres a dozen prints were supplied within four days. The sitter could for a further 24 livres buy the plate, from which 2000 prints could he pulled. By August 1789 Quenedey had learned enough about engraving to make himself independent. Chretien took a new artist partner, Fouquet, and later Fournier, and worked near the Louvre until his death. One hundred physionotraces by Fouquet and Chretien were shown at the Salon of 1793, and 600 two years later. Mme de Stael, Thomas Jefferson, Kosciusko, Louis XVIII, and many other celebrities sat to Quenedey, who sold their portraits at his shop. 
Although its procedures are mechanical and chemical, not photochemical, the physionotrace is a functional forebear of photography in that it served the needs of the middle class in the same way that photography would soon come to serve. Like the photograph, it challenged the unique art object. The physionotrace was mechanized, and it could be produced by persons of lesser talent and experience than possessed by miniature painters. The proliferation of physionotrace images augured the industrialization of the portrait that the photograph would accomplish. 
 Gernsheim, Helmut, and Alison Gernsheim. L.j.m. Daguerre: The History of the Diorama and the Daguerreotype. New York: Dover Publications, 1968. p. 117
 Marien, Mary W. Photography and Its Critics: A Cultural History, 1839-1900. Cambridge: Cambridge University Press, 2011. 44
Hanson, David Checklist of photomechanical processes and printing 1825-1910, 2017