Now, it is evident on the face of it that the transactions must have taken place in the presence of witnesses; otherwise a man who had made an awkward bargain would have found it easy to escape from his dilemma by denying that he had either given or received the penny. In early times, before writing became a common accomplishment, and when, as now, men might be eager to clinch a bargain without loss of time, it was desirable in the interests of common honesty that such agreements should be made in the light of day and in the face of the world. This custom appears to have continued to a late date. Thus, if O'Keeffe the dramatist may be believed, there was in the centre of Limerick Exchange a pillar with a circular plate of copper, about three feet in diameter, called "the nail," on which the earnest of all Stock Exchange bargains had to be paid. At Bristol there are said to have been four pillars called "the nails" in front of the Exchange, the purpose being the same; and similarly, at Liverpool, bargains were completed on a plate of copper, also called "the nail," and standing in front of the Exchange. It is probable, however, as Mr. Gordon observes, that, the phrase "payment on the nail" did not originate from circumstances like these, but was an adaptation of the Latin _super unguem_ or the French _sur l'ongle_, by which is meant "paying down into a man's hand." It might thus stand for a bargain the opposite of that of which God's Penny was the usual symbol. It appears to have been the custom at Ipswich in 1291 for traders not to make writings or tallies if two witnesses were in attendance to prove that the undertaking was to pay on a near day _ou freschement sur le ungle_. The notion of immediate payment is still conveyed by the expression, and would cover the entire amount, not merely God's Penny. However, that payment was undoubtedly made "on the nail;" hence some confusion may have arisen, especially where plates and pillars were provided for the deposit of earnest money. In all this there is much to remind us of the Roman _mancipatio_, a method of sale which demanded the presence of five witnesses, and in which the buyer took possession of his new purchase by holding in his hand a bronze ingot and repeating the formula: "This man [i.e., a slave] I claim as belonging to me by right quiritary; and be he [or he is] purchased to me by this ingot and this scale of bronze [i.e., that in which the purchase money had been weighed out]."