Delicate and precise, neatly arranged in alphabetical lemmas. I stumbled across the manuscripts in the Special Collections of the Leiden University Library, where they were listed in the inventory as ‘Adversaria of mixed content’. Without further explanation, except that their author was Jan Wagenaar. This eighteenth-century author was a household name in his time, writing about history, theology, and politics. Now here I was, looking at the notes he had used to write all those books, sermons, and pamphlets.The four leather-bound volumes contained pages and pages of lemmas on a variety of topics, from ‘concubines’ to ‘thatched roofs in the cities of Holland’. The lemmas included excerpts from a variety of texts, including snippets in French, English and Hebrew. This was how Wagenaar tried to organise his information flows, subsequently using this information to produce new texts.