The case studies in this volume juxtapose instances of knowledge exchange across a variety of fields usually studied in isolation anthropology medicine botany epigraphy astronomy geography philosophy and chronology. In their letters scientists and scholars tried to come to grips with the often unclear epistemological status of an observation a term which covered a wide semantic field ranging from acts of perceiving to generalized remarks on knowledge. Observations were associated with descriptions transcriptions copies drawings casts and coordinates and they frequently took into account the natural material linguistic historical religious and social contexts. Early modern scholars were well aware of the transformations which knowledge could undergo in the process of being communicated and therefore stressed the need for autopsy implying faithfulness fides and diligence diligentia to enhance the authority of observations. It was the specific character of Renaissance epistolography more than the individual subjects discussed which shaped the way information circulated. In the course of a correspondence the narrative in which observations were communicated could be modified by adding implicit or explicit considerations and by relegating lists drawings or tables containing raw material to appendices which recipients more often than not detached and filed separately. While letters were the prime medium for exchanging information they have to be studied in relation to notebooks drafts attachments and printed works in order to appreciate fully how observations were communicated within the learned networks of Europe during the sixteenth and seventeenth centuries.Contents IntroductionDirk van MiertGerhard HolkThe First Anthropologist of America Petrus Martyr de Angleria 14571526 and his Epistolary Reports De orbe novo decades octoCandice Delisle The Spices of Our Art. Medical Observation in Conrad Gessners LettersFlorike EgmondObserving Nature. The Correspondence Network of