Here's why:
* Sonnets have a specific structure: They are 14-line poems written in iambic pentameter with a specific rhyme scheme (usually ABAB CDCD EFEF GG or ABBAABBA CDECDE).
* "The Pulley" has a different structure: It has 10 lines and doesn't follow the strict sonnet format.
Therefore, "The Pulley" is classified as a short lyric poem, not a sonnet.