This curiosity is a 'human baby or animal mummy' bundle. It's presented in a miniature Victorian coffin-style display case. It was donated to the Museum in 1857 by Mr. Robert Walker with a label stating that it was the 'mummy of a cat'.
The mummified bundle contains no bones and it seems to be a 'fake' mummy, stuffed with clay, mud and plaster. It was probably constructed thousands of years ago, with a human style mask applied slightly later, and the case is clearly more modern. Whether the bundle ever contained anything sacred or was a deliberate attempt to mislead unsuspecting pilgrims is up for debate!