Swearing on the Book.
In testimony, oaths have always been associated with something to be touched or kissed. In England people used to kiss their thumbs instead of the Bible, and so supposed that they had saved their consciences. A rustic, in one of Mr. Meredith's novels says, "I swore, but not upon oath," meaning that he had kissed his thumb, not the book. Arthur Orton, in the Bush, laid his hand on a copy of Sheridan's plays, "which, though not a Bible, bore a cross." So Zeus lays his hand on the earth, in Homer, when he swears by that planetary body. People had to touch relics when they swore in the Middle Ages, as in the famous oath of Harold. The Danes, when they invaded England, were ready to take any oath with impunity, save that of touching a certain sacred ring or armlet. Hamlet made his comrades lay their hands on the blade of his sword.