J.K. Rowling
admitted, while writing a history of
cauldrons for Pottermore's
Harry Potter and the Half-Blood Prince chapter, that she considered making Hufflepuff's Horcrux a cauldron, and not the golden, two-handled cup that did appear in the final two books.
Quote:
J.K. Rowling: I did consider making Helga Hufflepuff's [Horcrux] a cauldron, but there was something slightly comical and incongruous about having such a large and heavy Horcrux; I wanted the objects Harry had to find to be smaller and more portable.