"But yet so difficult is the intellectual commerce, so narrow the intellectual fund, that the wisest men are frequently obliged to employ their money like counters, and their counters like money, in one case, however, without loss, in the other without fraud. We may be said to do the first, that is, to employ our money like counters, when we employ ideas of one kind to mark and suggest ideas of another. We employ, as it were, in this case, good and current money of one species, to compute and fix the sum payable in another: and thus guineas may stand in the place of shillings, or shillings serve to represent guineas."
— St John, Henry, styled first Viscount Bolingbroke (1678-1751)
(Essay I, §5; vol. iii, p. 444)
See "Letters or Essays Addressed to Alexander Pope, Esq." in the third volume of David Mallet's The Works of the Late Right Honorable Henry St. John, Lord Viscount Bolingbroke, 5 vols. (London : [s.n.], Printed in the Year 1754). <Link to ESTC><Link to ESTC>
Text from the third volume of The Works of the Late Right Honorable Henry St. John, Lord Viscount Bolingbroke, 5 vols. (Dublin: Printed by P. Byrne: 1793). <Link to Google Books>
Reading also in the 1967 reprint of The Works of Lord Bolingbroke, 4 vols. (London: Henry G. Bohn, 1844).