His brain was studied by Rudolf Wagner who found its weight to be 1,492 grams and the cerebral area equal to 219,588 square millimeters.[27] Also found were highly developed convolutions, which was suggested as the explanation of his genius.[28] Other brains that were removed and studied include those of Vladimir Lenin,[29] the mathematician Sofia Kovalevskaya,[30] and the Native American Ishi. The brain of Edward H. Rulloff, a noted philologist and criminal, was removed after his death in 1871; in 1972, it was still the second largest brain on record.[31]