During restoration works at the Santa Catalina de Siena Convent (Buenos Aires, Argentina), a small cloth bag was found in the central altar. It was embroidered with five equal armed crosses, and it contained the remains of an herb common in the region (Leersia hexandra). The bag was found along with a group of traditional Catholic votive offerings. According to the ethnographic information available, this bag was identified as a Guayaca. The historical antecedents, the ethnographic information and a possible interpretation of this kind of object and its decoration are analysed in this article. Multiple significant possibilities speak of the great complexity of African traditions incorporated into Creole society.