Depending on the way there are counted, there are thirteen or fifteen such shapes. Of two of these shapes, there are two versions, which cannot be made congruent using rotation. The Archimedean solids are named after the Ancient Greek mathematician Archimedes, who probably discovered them in the 3rd century BC. The writings of Archimedes have been lost, but Pappus of Alexandria summarized them in the 4th century. During the Renaissance, artists and mathematicians valued "pure forms" and rediscovered all of these forms. Johannes Kepler probably completed this search around 1620.