Sixty is the base number of the Sumerian number system, fully evolved in Mesopotamia (modern-day Iraq) by 3000 BC, and it remains the essence of how we measure time: sixty seconds in a minute, sixty minutes in an hour. The number is also the base of the 360 degrees of a circle, as in the fully imagined sky of the Sumerians (of which only a portion was ever visible from temple roofs), divided into six houses of 60 degrees. In Sumerian culture, the number 1 was expressed by a simple wedge, cut into clay or wood, and 60 by a great wedge. Sixty has the versatility of being neatly divisible by 30, 20, 15, 12, 10, 6, 5, 4, 3 and 2, and therefore makes for easy subdivision of irrigated land and the harvested crops which were initially gathered in sixty-fold sheaves, just as in pre-decimal English currency sixty pennies (60d) were a crown (five shillings/5s).
Barnaby Rogerson, Rogerson’s Book of Numbers: The Culture of Numbers from 1001 Nights to the Seven Wonders of the World
