John Napier
John Napier (1 February 1550 – 4 April 1617) was a Scottish mathematician, physicist and astronomer.
He was the author of A Plaine Discouverie of the Whole Revelation of St John,, a book which attracts the attention of Mr Norrell during a particularly tedious soirée he attends at the house of Mrs Godesdone.[4]
A Scotsman, Napier is perhaps best known to us for his ingenious observations on Mathematics; but in his own judgment this work interpreting the Revelation was the his magnum opus.
In his day Napier enjoyed the reputation of a "cunning man" and was broadly considered to be a magician, especially by the ignorant.* However, his published work does not demonstrate any depth of magical scholarship and we can be sure Mr Norrell would sniff at any such claim.
More may be found upon him here
* A story is related as to how he used his pet cockerel - sometimes thought to be his familiar spirit - to catch a thief among his servants. He placed his cockerel - which was black - in a darkened room, then bade his servants enter one by one and pet the bird, which would crow when touched by the thief. Unknown to them, he had covered the bird in soot, and upon inspecting the hands of his servants, determined the one with clean hands had been the one too afraid to touch the bird, lest his thievery be revealed. This was not magic, then, but ingenious trickery, although cleverly applied.