“Uma data central do calendário religioso dos Mandan, tribo que habitava às margens do rio Missouri, era o O-kee-pa, uma cerimônia de iniciação dos jovens que durava quatro dias.
George Catlin (1796-1872) registra esta cerimônia em sua viagem pelo Missouri em 1832, a respeito da qual escreve:
“”During the first three days of this solemn conclave, there were many very curious forms and amusements enacted in the open area in the middle of the village, and in front of the medicine-lodge, by other members of the community, one of which formed a material part or link of these strange ceremonials . . . The bull-dance . . . is repeated four times during the first day . . . and sixteen times on the fourth day; and always around the curb, or ‘big canoe’ [the drumlike structure in the center of the open area] . . . This subject I have selected for my second picture, and the principal actors in it were eight men, with the entire skins of buffaloes thrown over their backs, with the horns and hoofs and tails remaining on; their bodies in a horizontal position, enabling them to imitate the actions of the buffalo, whilst they were looking out of its eyes as through a mask.””
George Catlin, Letters and Notes, vol. 1, no. 22, 1841.”