An <u>allusion</u> is a literary device that makes an indirect <u>reference </u>to a particular historical event, person, place or a piece of work from any art.
Depending on his/her knowledge, a reader must find the <u>meaning</u> or multiple meanings of what is being referenced, as well as understanding the author's intention of using allusion.
The preposition of the sentence would be the word "of" since it relates the subject, the Incas, to the clause, which is "possessions with special knotted cords called quipu."