In Lewis Carroll's "Alice's Adventures in Wonderland," the Mad Hatter is known for his peculiar behavior and his never-ending tea party, which is a key scene in the story.
It's possible you're combining elements from different parts of the story, or perhaps you're thinking of a specific adaptation of Alice in Wonderland where a "Mad Vessel" might be featured.
Could you provide more context or details about where you encountered this term? That might help me figure out what you're referring to. 😊