The earliest remains of the opium poppy may have been found in west-central Europe because the fossil material was preserved in frozen peat. See M. D. Merlin, On the Trail of the Ancient Opium Poppy (Cranbury, N.J.: Associated Univ. Presses, 1984). M. Booth’s Opium. A History (London: Pocket Books, 1997) deals with opium in antiquity incompletely and inaccurately.