William Jones was a Welsh mathematician who taught mathematics on board ship between 1695 and 1702. After his travels, he became a mathematics teacher in London. The symbol π (pi), which represents the ratio of the circumference of a circle to its diameter, was first used by William Oughtred in 1647. William Jones later used the symbol in his book Synopsis Palmariorium Matheseos which was published in 1706. His book also included John Machin’s (1680-1751) calculations of the first 100 decimal places of π. Jones is believed to have used the Greek letter π because it was the first letter of the Greek word perimetron (περίμετρος] , meaning “perimeter”. The symbol was popularized by Euler in 1748.