ENThe Stammbuch (book of friendship), as an object but also as an "active participant" within numerous connections, played an integral part in building interpersonal relations (the concept of the causality of things) in the early modern period, becoming a peculiar social medium. An excellent example of one of the strands of this extensive social network were the educational contacts developed from the 16th century onwards between Basel and the Polish-Lithuanian Commonwealth. The main purpose of this article, therefore, is to present the rich social network that linked these two distant state organisms in the seventeenth century, using the remarkable book of friendship of the Basel burgher Reinhard Wasserhun (1586-1652), who undertook a traditional trip through Europe between 1612 and 1618 during which he visited the less popular destinations of the time, namely Central Europe (mainly the Polish, Prussian, Czech and Moravian lands). His journey allowed for the creation of new personal social networks which also form part of the European Republic of Knowledge. Keywords: Book of friendship; Kingdom of Poland and the Grand Duchy of Lithuania; Reinhard Wasserhun; Basel; social network; early modern times. [From the publication]