Heart Treasure, appendix "Concerning Meditation," in The Whole Works of the Rev. Oliver Heywood, B.A., vol. II (Idle: John Vint, 1825), p. 262

Think, O think often upon death, your own death; O that you were wise to consider your latter end; amongst all your thoughts, spend some upon your dying day, set a death's head before your eyes, and think to this purpose…