Charles Babbage

Here is a sketch (from Wikipedia) of Charles Babbage (b 26 December 1791).
He was the first to envisage a machine that could compute, though at the time this vision was of a purely mechanical device.
From http://en.wikipedia.org/wiki/Babbage
"He began in 1822 with what he called the difference engine, made to compute values of polynomial functions"
"The first difference engine was composed of around 25,000 parts, weighed fifteen tons (13,600 kg), and stood 8 ft (2.4 m) high. Although he received ample funding for the project, it was never completed"
"In 1991 a perfectly functioning difference engine was constructed from Babbage's original plans. Built to tolerances achievable in the 19th century, the success of the finished engine indicated that Babbage's machine would have worked"