In his rare free time on the Wisconsin farm, Muir was a prolific inventor. His ability to think mechanically benefited him in his early adulthood when searching for work.
William Fredrick Badé, wrote about the loafer chair in The Life and Letters of John Muir. "It was a wooden chair with a split bottom over which an awkward crosspiece had been nailed in front, apparently to cure the split, but really to make the sitter spread his knees. As soon as the supposed loafer settled down on the chair and leaned back, he pressed a concealed spring which fired a heavily charged old pistol directly under the seat." (Muiriana Collection, Loafer's chair)
For more information...
Read John Muir, Inventor, 1985 by George Emanuels.