Whose discovery of Ceres made the first-known dwarf planet the first object found in the asteroid belt?

Italian astronomer Giuseppe Piazzi spotted Ceres from Palermo on 1 January 1801. At the time, it was considered a planet because it seemed to fit the pattern between Mars and Jupiter. Later, many more small bodies were found in the same region, and Ceres became the largest object in the asteroid belt. In 2006 the International Astronomical Union reclassified it as a dwarf planet.