Early excavators neglected to perform thorough investigations of Sahure's monument, perhaps discouraged by its ruined state. In 1838, John Shae Perring, an engineer working under Colonel Howard Vyse, cleared the entrances to the Sahure, Neferirkare and Nyuserre pyramids. Perring was also the first person to enter the substructure of Sahure's pyramid. Five years later, Karl Richard Lepsius, sponsored by King Frederick William IV of Prussia, explored the Abusir necropolis and catalogued Sahure's pyramid as XVIII. The pyramid was re-entered later by Jacques de Morgan, but he too did not explore further. It then remained ignored for fifty years, until the Egyptologist Ludwig Borchardt visited the site.