Ars Technica introduced me to the inventor of the equals sign. I was surprised to read that it was a 16th century Welsh scholar who came up with this symbol, since so much of our algebraic foundations was passed on through and from Arab scholars in the Middle Ages. Anyway, here’s a quote from the man we’re talking about:

And to avoide the tediouse repetition of these woordes: is equalle to: I will sette as I doe often in worke use, a paire of paralleles, or Gemowe lines of one lengthe, thus: = , bicause noe .2. thynges, can be moare equalle..

More about the life of Robert Recorde can be read in the Wikipedia, of course. He must have been quite a character: he taught mathematics in Oxford in his youth, went on to study medicine, then became a “controller of Mint” in several places. He also wrote the first English book on Algebra, called “*The Grounde of Artes*“, and later followed up with a book that introduced the equals sign (his invention) as well as the symbols for plus and minus that were already in use in Germany.

One of the commentators on the Ars article says the text of this 1557 work is transcribed in the Gutenberg Project; unfortunately, that’s wrong. A copy of “*The Whetstone of Witte*” can be found in the Internet Archive.