The quote today comes from Harold Raeburn, a Scottish hardman of the late 1880s and early 1900s. He put up many rock routes on Ben Nevis, the first winter ascent of Observatory Ridge, and he was the climbing leader on the 1921 Everest recon.
"Think of everything you could want on a climbing expedition, say, of thirty hours. Cut out from this all you think might be fairly easily dispensed with. Take with you 50% of the remainder."