The time and place under analysis, 19th century Brazil, constitutes a privileged moment for the historiographer of linguistics attentive to the methodological requirements of his/her craft. It is an important point in time of reaffirmation of a Brazilian identity and of the increase of interest in the indigenous languages of Brazil, manifested by the re-edition of their classical texts, grammars and dictionaries, followed by a wave of scientific expeditions that produced original materials. This paper attempts to establish a link between the first efforts to set up a typological classification of the native languages and to illustrate the individual biases that entered into these scientist-travelers’ analysis. Particular attention will be paid to an investigation of the status ascribed to the so-called Brazilian and Paraguayan ‘general languages’; respectively, the Tupí and the Guaraní.