TheLiber de orbe, attributed to Māshā'allāh (fl. 762–ca. 815) in the list of Gerard of Cremona's translations, stands out as one of the few identifiable sources for the indirect knowledge of Peripatetic physics and cosmology at the very time Aristotle's works on natural philosophy themselves were translated into Latin, from the 1130s onward. This physics is expounded in an opening series of chapters on the bodily constitution of the universe, while the central section of the treatise covers astronomical subjects, and the remaining parts deal with meteorology and the vegetal realm. Assuming that Gerard of Cremona's translation of theLiber de orbecorresponds to the twenty-seven chapter version that circulated especially during the thirteenth and fourteenth centuries, it was, however, not this version, but a forty-chapter expansion thereof that became influential as early as the 1140s. It may have originated in Spain, as indicated, among others, by a reference to the difference of visibility of a lunar eclipse between Spain and Mecca. Unlike the twenty-seven chapterLiber de orbe, this expanded and also partly modified text remains in manuscript, and none of the three copies known so far gives a title or mentions Māshā'allāh as an author. Instead, the thirteenth-century witness that is now in New York attributes the work to an Alcantarus:Explicit liber Alcantari Caldeorum philosophi. While no Arabic original of the twenty-seven chapterLiber de orbehas come to light yet, Taro Mimura of the University of Manchester recently identified a manuscript that partly corresponds to the forty-chapter Latin text, as well as a shorter version thereof.