Well, after a short search, I came upon this:Classical art (mostly on Greek vases) shows Atlas holding the celestial spheres, not the terrestrial globe, like people thought. The solidity of the marble globe borne by the Farnese Atlas (statue from ca. 150 CE) aided the misconception, reinforced in the 16th century by the developing usage of atlas to describe a corpus of terrestrial maps.
So the misconception originated as soon as the first pictures of Atlas and the celestial spheres were made on vases, so at least since 530 BCE.
Well, I’ll keep thinking about it and maybe come up with something better.