The roots of the tiny house movement can be traced to 19th-Century US naturalist and essayist Henry David Thoreau, whose book Walden (1854) is an inspiring meditation on simple living in natural surroundings. Jay Shafer, the "godfather of tiny houses", spearheaded the modern movement when he built a tiny house on wheels and wrote The Small House Book in 1999. Shafer founded the Tumbleweed Tiny House company, before leaving to focus on social justice and housing rights.