Note 22 — Front matter
Reading edition
Abulcacim Abnacahm, Libros del saber, edition by Rico y Sinobas, Madrid, 1866, vol. 3, pp. 241-271. The design of the instrument has been very fully discussed by A. Wegener, "Die astronomischen Werke Alfons X," Bibliotheca Mathematica, 1905, pp. 129-189. A more complete discussion of the historical evolution of the equatorium is given in Derek J. Price, The equatorie of the planetis, Cambridge (Eng.), 1955, pp. 119-133.