If, during the course of the game, it be discovered that any error or illegality has been committed in the moves of the pieces, the moves must be retraced, and the necessary correction made, without penalty.
Howard StauntonThe Pawn moves only one square at a time, and that straight forward, except in the act of capturing, when it takes one step diagonally to the right or left file on to the square occupied by the man taken, and continues on that file until it captures another man.
Howard Staunton