« All the sons of Alan Qo'a used to be born with red-gold hair and blue eyes, but this child [Kublai] is swarthy like his maternal uncles. »

— Rashid al-Din, Compendium of Chronicles (Jami'u't-tawarikh), traduit par W. M. Thackston, Harvard University, 1998, Part 2, p. 427.