Browsing through Walten’s notes also helped Jagersma to get to know the pamphleteer better, even though he is been dead for three hundred years. “The Memoriaelen say a lot about him. I could read how Walten did his research, follow his fascinations, and see the ideas for pieces he was not able to work out anymore. In a way, these two notebooks are a kind of self-portrait.”

At the National Archives in The Hague, Jagersma was able to recover two documents that historians believed to be lost. These were the notebooks of Ericus Walten. These manuscripts had been confiscated by a court, the High Court of Holland, when Walten was arrested in 1694.