“Two mysterious processes—the rubefaction and albefaction of waters, i.e. reddening and whitening or clarifying a liquid . . . are referred to in medieval textbooks of alchemy. . . .

It was part of the theory that when the ingredients began to turn yellow they were on the verge of becoming the Philosopher’s Stone, by which all could be turned to gold. The Philosopher’s Stone was held to be heavy, sweet-smelling, constant and pink, and to exist in powder form as well. . . .”

—Neville Coghill, endnotes from his translation of Geoffrey Chaucer’s The Canterbury Tales, 1952.