The position is taken from the simultaneous display Emanuel Lasker - Loman, London 1910
Black to move AND WIN!
1...Rc4+!! 2.Kg5 Rh4!! the only move preventing White's promotion of the h pawn. 3.Kxh4 g5!! freeing the g7 square for the King 4.Kxg5 Kg7
The source of this endgame is "Van Perlo's Endgame Tactics" excellent book.