Aside -- I was a little confused, I'd only ever seen it spelled "Quipu" before. I assumed it was a Spanish or Portuguese word and shouldn't need to be transliterated (thus the multiple spellings). It's not -- it's a word from the native Peruvians and therefore does need transliteration.
From the wikipedia article [1]:
> Quipu is the Spanish spelling and the most common spelling in English.[citation needed] Khipu (pronounced [ˈkʰipu], plural: khipukuna) is the word for "knot" in Cusco Quechua; the kh is an aspirated k. In most Quechua varieties, the term is kipu.
From the wikipedia article [1]:
> Quipu is the Spanish spelling and the most common spelling in English.[citation needed] Khipu (pronounced [ˈkʰipu], plural: khipukuna) is the word for "knot" in Cusco Quechua; the kh is an aspirated k. In most Quechua varieties, the term is kipu.
[1] https://en.wikipedia.org/wiki/Quipu