On this day in history, 18th June 1558, the will of Robert Recorde, the Welsh mathematician, physician and mint administrator, was proved. His date of death is not known, but he is thought to have died in mid-June 1558.
Recorde is known for introducing the "equal to" sign, i.e. "=". He published several mathematical works, including The Grounde of Artes, teachings the Worke and Practise, of Arithmeticke, both in whole numbers and fractions in 1543, which was the first book on Algebra published in England, and The Whetstone of Witte, whiche is the seconde parte of Arithmeteke: containing the extraction of rootes; the cossike practise, with the rule of equation; and the workes of Surde Nombers, in which he introduced the "=" sign.
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