John Canaparius was a Roman monk at Alexius cloister. It had long been assumed that in the year 999 he wrote the first 'Vita Saint Adalberti', or 'Life of St. Adalbert of Prague' just two years after Adalbert's death.
Adalbert was sent by the pope to convert Prussia to Christianity and had come to Prussia apparently taking the route along the Vistula river to reach the Baltic Sea at the later city of Danzig, which long before becoming a city, had been a small trading and fishing settlement. This settlement was supposedly recorded by Canaparius.
It is however now assumed, that the 'Vita' was not written by Canaparius, but was written down in Luettich, with the oldest tracable version having been at the imperial Adalbert shrine at Aachen. Bishop Notger of Luettich, a hagiographer himself, apparently had knowledge of the earlier handwritten Vita from Aachen. The imperial court at Aachen had in 997 assembled immediately upon receiving word of Adalbert's death and had thereupon planning the upcoming events.
Saint Adalbert was the first missionary in Prussia and later he became the main patron saint of the Königsberg Dome.