In Walten’s two notebooks, referred to as Memoriaelen, Jagersma discovered a lot of details about the pamphleteer’s life. “These notebooks look a bit like the Moleskine notebooks that we know today,” says Jagersma, “but thicker, and bound in parchment.” In the more than five hundred pages, Walten collected all kinds of information. Jagersma lists the categories: “Personal anecdotes, philosophical and theological reflections, ideas, incursions, medical recipes, accounts of alchemical experiments, but also departure and arrival dates of the trekschuit (sail- or horse-drawn boat). The notebooks also contain lists of books he still wanted to read.”