I've seen far lower estimates of Charles Curtis' (technical) indian ancestry.
http://www.answers.com/topic/charles-curtisThe claim that Curtis was 3/8th Indian rests on the following calculation:
His father's white. His mother's mother was Indian, though mixed tribe (well duh, these nations were smallish and not endogamous, at least not their well connected chiefly castes). His mother's father was mixed-blood.
This ignores the fact that his mother's father was basically a white man (French Indian trader) with some slight indian ancestry, and the same *seems to* go for his mother's mother's father - it's his mother's mother's mother who was fullblooded Indian. That makes him some unspecifiable bit above 1/8th Indian.
And is probably not untypical for the actual pedigree of White people that like to talk up their partly Indian ancestry. (Or Black people, for that matter.)