Nicolas Régnier, c. 1626, is aware it should be Pandora's jar, not box.
The mistranslation of pithos as "box" is usually attributed to the sixteenth century humanist Erasmus of Rotterdam when he translated Hesiod's tale of Pandora. Hesiod uses the word "pithos" which refers to a jar used to store grain. Erasmus, however, translated pithos into the Latin word pyxis, meaning "box". The phrase "Pandora's box" has endured ever since.