This article examines the sources of literary invention in Philtron, a treatise in verse on the theme of Christian love by the Polish and neo-Latin Renaissance poet Sebastian Fabian Klonowic. To get a better appreciation of his work it is necessary to look at his sources, especially books of humanist erudition, learned compendia, dictionaries, handbooks of rhetoric, anthologies and commonplace books. An analysis of his use of those sources in Philtron and an examination of his notes indicate that Klonowic probably did not read all of his books through from beginning to end. Some of his readings were intentionally selective. In particular, while collecting material for his treatise, he would mine the grand 16th-century reference books like Ambrogius Calepinus's multilanguage Dictionarium, Dominico Nani's anthology Polyanthea, or Erasmus' Apophtegmata. The argument and topoi in at least some parts of Philtron are much indebted to the contemporary compendia and erudite research.