I want to know the answer to the following question:
What was the name of the 83.5 kg stone that symbolized the Unspunnenfest, first held in 1805?
All the background I'm provided with is that "It is also central to the Unspunnenfest, first held in 1805, with its symbol the 83.5 kg stone named Unspunnenstein.". Is that enough to answer the question?