Who, after being lured by Prince Felix Yusupov and the Grand Duke Dmitri Pavlovich to the Yusupovs' Moika Palace on 16 December 1916, was poisoned with cyanide, shot 4 times, beaten and drowned in the Neva River (where he had tried to claw his way from under the ice) but was reported to sit up on his burning funeral pyre?