It is not clear when Gray started working on the telautograph. The earliest allusion I found in Gray’s own publication Experimental Researches in Electro-Harmonic Telegraphy and Telephony, published in 1878. In parts written as a diary, the text mentions Gray’s “experiments upon the general subject-matter of transmitting and receiving electrical vibrations” (1878: 33). In an entry entitled “Return to Chicago – Resumption of Experiments – 1874,” he formulates possible applications of this type of research:

[…] Up to this point my experiments had been mostly of a general character, with a view to determine in what line to first direct my efforts; for, as I have before stated, I foresaw as early as May [of 1874] the probable outcome of the invention in several of its ramifications; more particularly I saw its immediate application in the direction of multiple Morse telegraphy; its adaptation to a printing system, an autographic system and the transmission of spoken words. (1878: 33; emphasis added)

Although made in the context of his work on the telephone, this quote for the first time reveals Elisha Gray’s long-time vision of an “autographic system” or telegraphic signing and handwriting device. It also reveals that, in 1874, at least the core of the future telautograph already existed, what Gray calls “the invention.”

The Swiss inventor Gustav Adolf Hasler (1830-1900) described in 1873 an electric pantograph which transmitted the movement of a pen over telegraph. [Gustav Adolf Hasler, “Pantographe éléctrique.” Journal télégraphique 2.22 (October 1873): 344-46.]