After a short literature review on archaeoastronomy and ethnoastronomy, the article looks at some works from the end of the 19th century that provide information on the ethnoastronomy of Brazilian indios. These reports are written by Canadian naturalist Charles Frederick Hartt (1840-1878) and Brazilian polimate José Vieira Couto de Magalhães (1837-1898). Although shaped by the cosmons of their authors and the scientific theories of the ethnology of the time, they register a small fraction of indigenous knowledge systems about nature, their celestes myths, constellations and calendars. The authors are contemporary and corresponded, but independently registered some knowledge common to the peoples who spoke a Tupi language.