al- ال ʻAzzārī, Khalīl ibn Ibrāhīm, active 19th century عزاري, خليل ابن إبراهيم. Mansuri Collection (Library of Congress) text xx 18uu monographic [18--] ara

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19 leaves (24 lines), bound : paper ; 24 x 17 cm. This 19th-century manuscript is a treatise on gnomonics, the mathematical discipline concerning the calculation of the projection of shadows for timekeeping purposes. The relatively recent date of the work attests to the great and lasting importance attributed in the Islamic world to the reckoning of time through the observation of shadow lengths. The use of gnomonics and the construction of sundials were perceived as the most religiously correct way to calculate the right times of prayers, since religious texts already define the midday (zuhr) and afternoon ('asr) prayers in terms of shadow lengths. This treatise is devoted to one particular kind of sundial only, the munharifa (literally "inclined") or vertical sundial, but Islamic tradition records a vast number of treatises that also describe the so-called horizontal sundial (known as ruhāma or basīta). The tradition of treatises about sundials began in the ninth century with the set of tables for the production of sundials created by the famous mathematician and astronomer Muḥammad ibn Musá al-Khuwarizmi (active 813-46). The work presented here begins with a general description of the shape and features of vertical sundials, which is followed by tables for the appropriate construction and positioning of sundials. The tables are outlined in black and red ink and can be seen on some of the early folios. In some cases these tables occupy a complete manuscript page. World Digital Library. Binding: modern cardboard covered with cloth, leather spine. Fol. 1a-19a. Library of Congress. Mansuri Collection, 5-766. Ms. Nastaʻliq script; 13-25 lines in written area, 17 x 10 cm. Paper: yellowed cream, with torn edges, in moderate condition. Watermark on leaf 20. Black and red ink in text. Title written in later hand in pink ink. Catchwords only on leaves 1 and 7. Starting from the third leaf, each verso begins with the last word in the previous recto. Tables: leaf 3 verso, leaf 5 verso, leaf 7 verso, leaf 9 recto through 10 recto, leaf 13 recto. Incipit: نحمدك اللهم يا من مددت الظل عرضا و طولا و لم تجعل ساكن جعلت الشمس عليه . . . Also available in digital form on the Library of Congress Web site. Also available in digital form on the Library of Congress website. Purchase ; Mahmud al-Mansuri ; 1945. Arabic. n-us-dc Astronomy, Arab Manuscripts, Arabic Washington (D.C.) Sundials Time measurements QB215 .A99 1800z https://hdl.loc.gov/loc.amed/amedscd.2008401692 2008401692 aacr DLC 080617 20250607024424.8 15333178 Converted from MARCXML to MODS version 3.8 using MARC21slim2MODS3-8_XSLT1-0.xsl (Revision 1.172 20230208)