A two-dimensional abacus—the Papy Minicomputer
Jean Van Arsdel, Joanne Lasky · The Arithmetic Teacher · 1972
Whitehead has written, “It is a profoundly erroneous truism … that we should cultivate the habit of thinking of what we a re doing. The precise opposite is the case. Civil ization advances by extending the number of important operations which we can perform without thin king about them” (Whitehead 1920, p. 6 1).