Three: History & Examples
Commonplace books (or commonplaces) are a way to compile knowledge, usually by writing information into books. They have been kept from antiquity, and were kept particularly during the Renaissance and in the nineteenth century.
#HeyPresstoConf20

The following all had/kept commonplaces:

Charles Darwin
Francis Bacon
Ben Jonson
John Milton
Mrs Anna Anderson
E.M. Forster
John Locke
W.H. Auden
H.P. Lovecraft
Virginia Woolf
Joseph Conrad
Washington Irving
Victor Hugo
Isaac Newton

Isaac Newton, a mathematician and physicist, used a “Waste Book” to write his initial conceptualization of the calculus. A digitized copy of this commonplace is held at the University of Cambridge and is freely available to view online.