Even though those results invalidated his original argument for the feasibility of perpetual motion, 's Gravesande continued to defend Bessler's work, claiming that Bessler might have discovered some new "active principle" of nature that allowed his wheels to keep turning. Similar views were defended at the time by Gottfried Wilhelm Leibniz, Johann Bernoulli, and others, but the modern consensus is that Bessler was perpetrating a deliberate hoax. Russian Tsar Peter the Great was interested in Bessler's wheel and sought 's Gravesande's advice on the subject.