CELERY SOUP

1/2 stick celery, 1/2 small onion, 1/4 oz. butter, 1 potato, pepper and salt. Wash, peel, and cut up the vegetables, and cook them in 1/2 pint of water till tender. Rub through a sieve, return to the saucepan, season with pepper and salt, add the butter, boil up, and serve.