According to modern Franciscan historians, this report by Serra to the Inquisition is the only letter of his that has survived from eight years of mission work in the Sierra Gorda. Serra's first biographer, Francisco Palóu, wrote that Serra, in his role of inquisitor, had to work in many parts of Mexico and travel long distances. Yet the Archivo General de la Nación in Mexico City, with over a thousand volumes of indexed documents on the Inquisition, apparently contains only two references to Serra's work for the Inquisition following his 1752 appointment: his preaching in Oaxaca in 1764, and his partial handling of the case of a Sierra Gorda mulatto accused of sorcery in 1766.