Urton, Gary. Signs of the Inka Khipu: Binary Coding in the Andean Knotted-String Records. Austin: University of Texas Press, Austin, 2003.
roughly 600 extant; most looted from graves in 19/20c
frequent mention in Spanish chronicle after Conquest, begun in 1532
khipukamayuq — knot-maker/keeper
primary cord, sometimes with end dangle; pendants that may have subsidiary or tertiary pendants off them; top cord going the other direction
should khipu be considered mnemonics, or form of writing? aid recall of specific administrator, or conventionalized way of sharing information?
if just mnemonic, like string around finger, rosary, or memory theatre can never recover meaning — idiosyncratic, not generalizable
but earliest cuneiform were bookkeeping with logogram mnemonics; khipu could be similar