The first missionary expedition from the years 1730-31 occupies a special place in the annals of Institutum Judaicum et Muhammedicum. It made such a big impression on its participants and the founder, Johann Heinrich Callenberg, that it started missionary peregrinations that lasted for more than 50 years. That mission was the idea of Georg Widmann, who previously travelled across Germany, Poland and Hungary for two years with a private mission among Jews. He described it in the missionary autobiography attached to this article, written at Callenberg's request. In the course of his missionary wandering, Widmann came across the Land Rabbi of Wielkopolska, Jaakow Mordechej ben Naftali ha-Kohen, who, by Widmann's account, got to appreciate highly the Institute's publications. Upon receiving an informal approval from the Land Rabbi, Widmann went to Halle and assured Callenberg that many Jews in Poland were leaning toward Christianity. They were not abandoning the Judaic faith, however, because they did not want to sever ties to their people and preferred to work covertly on converting the rest. He guaranteed that the Institute's publications could be distributed in Poland. He also insisted that it was necessary to convince the Land Rabbi to move to the Evangelical church, together with his followers. Callenberg accepted Widmann as his associate and consented to his travel to Poland in the capacity of the Institute's representative. Theology Student Johann Andreas Manitius was to accompany Widmann and verify his accounts. The expedition ended in a fiasco, with the rabbi refusing to enter an Evangelical church and urging the Jews to burn the Institute's publications. However, this did not deter the Institute's collaborators, who continued such missions until the 1780s.