an excerpt from Richard Feynman's The Douglas Robb Memorial Lectures - Part 1 -- where Feynman discusses the difference between "Philosophy" and 'Modern Science and Mathematics' using the example of Mayan calculations of Venus synodic period, involving counting of 584 pebbles (365 * 8 / 5) = 2920 / 5 = 584 days

the full video can be found at Vega website:
http://www.vega.org.uk/video/programme/45
( the particular video excerpt concerned here is @ 00:30: 00 to 00:34:35 )

More on Venus synodic period:
http://www.johnpratt.com/items/astronomy/eve_morn.html