The io9 article cites Blood Work: A Tale of Medicine and Murder in the Scientific Revolution, by Holly Tucker (2011) as the source for the story. "If William Thornton [pictured], physician and designer of the US Capitol, had had his way, Washington's body would have been subjected a scientific experiment designed to bring the deceased former president back to life," writes Lauren Davis. "... he planned to perform a tracheotomy so he could insert a bellows into Washington's throat and pump his lungs full of air, and finally to give Washington an infusion of lamb's blood. Friends and family declined Thornton's mad scientist offer..."
Lamb's blood, apparently, was thought at the time to have regenerative properties -- or at Thornton wanted to investigate the possibility, good Enlightenment scientist that he was. He probably deserves the benefit of the doubt, since medical science was primitive at the time, and at least he wanted to investigate new avenues of research, however strange they might sound to us.
A couple of other outlets have picked up the story, including the Daily Mail, which in true British tabloid style called its article, "Zombie George Washington: How a mad scientist planned to reanimate the first president with lamb's blood after he died."