According to the experts , drawings on the back of paintings is `` extremely rare , '' and none have been found so far that can be attributed to da Vinci . Three sketches found under the da Vinci paintings . Work continuing to determine if the drawings were by da Vinci . Drawings are a horse 's head , a partial skull and infant head with beard .
Three sketches found under the da Vinci paintings . Work continuing to determine if the drawings were by da Vinci . Drawings are a horse 's head , a partial skull and infant head with beard .