Théodule Devéria help Mariette read inscriptions in Cairo and its surroundings. He tried to accurately document the archaeological sites using drawings, stampings and photographs. His calotype pictures from this trip are often poor in quality, showing a lack of technical skills. In 1860 he was appointed preserving assistant at the Louvre's Department of Egyptology. He revisited Egypt in 1861–62, traveling up the Nile to Philae at the First Cataract, and into Nubia to the Abu Simbel temples. After returning he helped Mariette prepare descriptions of the excavation in Egypt in 1850–54 for publication. In November 1864 Devéria met the future oriental scholar
Abu Simbel temples a way that on October 22 and February 22, the rays of the sun would penetrate the sanctuary and illuminate the sculptures on the back wall, except for the statue of Ptah, a god connected with the Underworld, who always remained in the dark. People gather at Abu Simbel to witness this remarkable sight, on October 21 and February 21. These dates are allegedly the king's birthday and coronation day, respectively. There is no direct evidence to support this. It is logical to assume, however, that these dates had some relation to a great event, such as the jubilee celebrating