Ready reckoner

They were widely used in shops and by tradesmen before the advent of cheap electronic calculators, metric weights and measures and decimal currencies in the 1970s.

The earliest surviving ready reckoner in English dates from the 1570s;[2] other sources attribute the invention to the Dutch mathematician Simon Stevin, who calculated and published decimal tables in the 1580s.

The most popular of these was William Leybourn's, Panarithmologia, being a mirror breviate treasure mate for merchants, bankers, tradesmen, mechanicks, and a sure guide for purchasers, sellers, or mortgagers of land, leases, annuities, rents, pensions, &c. in present possession or reversion.

[6] This was a modernised and extended version of Leybourn's work, which was reprinted in Boston, Massachusetts, about 1770, and translated into German in Germantown, Philadelphia, 1774.

By the end of the eighteenth century, ready reckoners designed for the needs of particular trades or types of business began to appear.