This video explains interesting aspects of the Incan culture, such as the fact that they kept records by using strings with knots tied in them and the fact that the society was governed in units of “ten”— where groups of ten people were subdivided into groups of ten groups, with those groups being further subdivided in such a manner.  The Incas practiced human sacrifice with willing subjects, and they mummified their leaders who they continued to bring to meetings as corpses.  The video then explains the complicated rules for succession that the leaders used.