"If the Treasury were to fill old bottles with banknotes, bury them at suitable depths in disused coalmines which are then filled up to the surface with town rubbish, and leave it to private enterprise on well-tried principles of laissez-faire to dig the banknotes up again", in Keynes, Volume III, capitolo 10, sezione 6, p. 129. (EN) John Maynard Keynes, The General Theory of Employment, Interest and Money, Londra, Macmillan, 1936.
