In this chapter I provide an edition, with an apparatus of different readings and comments, of the partial text of René Descartes’s Traité de l’homme conveyed in a Latin translation by the manuscript ATH 1444, now extant at the Bibliotheca Thysiana at Leiden (part of the Leiden Universiteitsbibliotheek), and titled Tractatus de homine a Cartesio. The readings are considered with respect to the Latin and French editions published by Florentius Schuyl (1662 and 1664) and Claude Clerselier (1664 and 1677). This transcription offers an overview of the differences between the foremost known versions of the treatise, tracing to (possible) author’s and editors’ interventions, with particular attention to those concerning conceptually loaded terms, errors in translation or transcription, references to (now) missing figures, and stylistic choices.