This pencil drawing shows the circular window in the qibla wall of the mausoleum of the Sultan Hasan Mosque in Cairo. The window is divided by a horizontal band with a pattern of circles. Like the lateral windows of the façade (IG_294), the upper part has a pattern of circles and flowers.
Pascal Coste drew only half of the window and made several annotations regarding the materials.

Between 1818 and 1827, Pascal Coste documented the buildings in Cairo extensively, among them the Sultan Hasan Mosque (757–764 AH / 1356–1363 CE). Two preparatory works for his publication Architecture arabe ou Monuments du Kaire, Mesurés et Dessinés, de 1818 à 1826 (1837) are dedicated to the windows of this mausoleum (see IG_202). The present drawing shows a circular window, and a second one of the lateral windows in the qibla wall (IG_294).
Another preparatory work, a watercolour (Victoria and Albert Museum, SD.272:14, IG_130), shows the wall lightly coloured. This colouring corresponds only approximately to the colour indications of the present drawing. So, for instance, the blank round pieces of glass indicated appear in a reddish colour.
The windows of the mausoleum of the Sultan Hasan Mosque were remade on the model of the old ones in 1906 (see Related Location).
Circular stucco and glass windows have a long tradition, going back to Ayyubid and Mamluk times (see Flood, 1993, p. 83, fig. 40, 44). In Cairene mosques, they were often placed above the mihrab (see IG_188).