The equal sign--and poetry--from Robert Recorde

  A poetic introduction of the equal sign (by Robert Recorde): 

This image is an excerpt from Recorde's The Whetstone of Witte (1557)

    Robert Recorde was born in Wales around 1510-12; he taught mathematics at both Oxford and Cambridge and got his MD from Cambridge in 1545 -- and became a physician to royalty.  He published a number of mathematical works -- one of the best known being The Whetstone of Witte (1557) -- a photographic copy of several of its pages is available here. He is lauded for the invention of the equal sign, first appearing, as shown above, in The Whetstone of Witte.  -- This article from 2015 in WalesOnline cites Recorde's greatest achievement to be making mathematics accessible to a general reader.   

Mathematics expressed as poetry -- by Robert Recorde

A lot more of the history of mathematical notation is available here.