Author: NUNES, Pedro.
Title: De crepusculis liber unus, nu[n]c rece[n]s & natus et editus.Including: [Abu 'Abd Allah Muhammad ibn MU'ADH] (mis-attributed to Ibn AL-HAYTHAM). De causis crepusculorum liber unus, à Gerardo Cremonensi iam olim Latinita te donatus, nunc vero omniu[m] primum in lucem editus.(Colophon: Lisbon, Ludovicus Rodericus, January 1542). 4to. With woodcut architectural title-page with an arch containing putti and mythological figures (including 2 winged female fauns holding drapery, with the Royal Portuguese coat of arms at the foot and an armillary sphere at the head, 40 woodcut diagrams concerning astronomy, spherical geometry, optics and geodessy in the text, Rodericus's spectacular full-page emblematic woodcut device (a dragon with the motto "salus vitae" on a banderole), numerous woodcut initials (several series), and a vine-leaf ornament (a variant of Vervliet 94?). Set mostly in the first successful italic type to have sloped capitals, cut by Peter Schoeffer the younger, but with extensive passages in roman. Bound in a period-style Italian calf binding, gold-tooled spine, each board with a blind-tooled frame and a gold-tooled centrepiece, with "Petri Nonii" on the front and "MDXLII" on the back.
Description: [73], [1 blank] ll.First edition of two of the most important and rarest scientific works on twilight and optics. The first is a work from Portuguese soil, written by the greatest Portuguese mathematician Pedro Nunez (1492-1577), who served as royal cosmographer at the court of João III. His De crepusculis discusses new solutions for problems concerning twilight (for example the shortest twilight) and the refraction of light, and announces his new instrument for measuring exceedingly small angles, now called a “nonius”.The title-page attributes the second work, De causis crepusculorum, to “Allaken”, meaning the greatest Islamic physicist Ibn Al-Haytham (965-1039), living in the Arabian Peninsula, whose seminal work in optics broke with ancient Greek theories. In fact, it is now attributed to the great 11th-century Andalusian mathematician, father of spherical trigonometry and astronomer Abu ’Abd Allah Muhammad ibn Mu’adh, described by Averroës as “advanced and high-ranking” (Sabra, p. 85), though we know very little about him. His work discusses the density of the atmosphere and establishes a relationship between atmospheric pressure and altitude. It also notes that twilight only ceases or begins when the sun reaches 19 degrees below the horizon. It was translated from Arabic into Latin by Gherardo da Cremona (1114-1187), who brought Arabic science to the West. As an artifact it shows the significant and crucial contributions Islamic civilisation made to the accumulation of scientific knowledge in the pre-modern age, the golden age of Arabic science, though the Latin translations in this field only provide “a dim reflection of the true splendour of achievements” (Gerli, p. 804).With an owner's inscription at the head of the title-page and a handwritten imprint on the title-page in the same hand, three faint library stamps (two from a library in Douai) and with traces of a bookplate removed from the front paste-down. Binding very slightly worn around the spine, some small stains on the endpapers, but otherwise a beautiful copy in very good condition.l Adams N375; DSB X, pp. 160-161; Honeyman 2353; Houzeau-Lancaster 1188 & 2473; King Manuel 48; Palau 196748; Poggendorff II, col. 305; Sabra, “The authorship of the Liber de crepusculis”, in: Isis, 58 (1967), pp. 77-85; Stilwell 781 & 863; USTC 344785; cf. Carmody, Arabic astronomical and astrological sciences in Latin translation; Gerli, Medieval Iberia (2003), p. 804; not in Vagnetti.

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