Nicholas Saunderson (1682-1739) was an extraordinary mathematical talent—he was also blind (from about the age of one), and invented, principally for his own uses, what I think is the first mathematical calculator designed specifically for the use of the blind. He was supremely gifted and creative, and rose to become the fourth Lucasian professor at Cambridge, succeeding the expelled William Whiston, who had in turn succeeded Isaac Newton—Saunderson also held the post for one of the longest periods of time, 1711-1739. HE was friend and associate to Newton, Whiston, Roger Cotes, Halley, De Moivre and others during a particularly rich intellectual period in the history of physics and the maths. 
His calculator was smart and simple, based on a cribbage-board –like device, that was able to perform arithmetical and algebraic functions—it consisted of nine rows and was worked with two pins, the positioning of the pins on the engraved board telling the user their value. (There was another calculator for the blind constructed by Meyer (below, left) using a sort of reverse principle to the Saunderson model where it was the shape and placement (leaning or not, for example) of the pegs in the hole that annotated value rather than their placement on the board.
The Saunderson computer was described in his The Elements of Algebra…,1 published at Cambridge in the first edition just after the author’s death, in 1740. The device was described in the book by John Colson (who succeeded Saunderson to the Lucasian chair), who commented that it was via the use of the device that Saunderson could compose his treatise on algebra. (At right is another Saunderson-based calculator allowing for the construction and study of geometrical figures).
[Image source for Saunderson portrait: https://en.wikipedia.org/wiki/Nicholas_Saunderson#/media/File:Nicolas_Saunderson.jpg]
Notes:
!. Here's a link for a later-n-the-century (1792) edition of the Saunders book via the Internet Archive: https://archive.org/details/selectpartsofsau00saun
Also see MacTutor History of Mathematics biography of Saunderson, here: http://www-history.mcs.st-and.ac.uk/Biographies/Saunderson.html
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