[The postcard in Brazil in the early twentieth century: a medium on which image and action combine]

This article seeks to highlight the postcard as a medium on which an image and the action of someone commenting on the image come together. Four postcards that have been used as sources in historical research are discussed. Absorbed by the practice of photography, the study first focuses on the artist. Then it focus on the role of the model. Finally, it presents the incorporation of the sender and his message. When doing so, it recognizes the surface of this medium as a space for transparency in terms of the social relationships prevailing in Brazil in the early twentieth century. The article also suggests that Manuel Querino was the first intellectual to use a postcard as a bibliographic source.