Combine flour, nutmeg and salt; mix well and set aside. In large mixing bowl, cream butter and sugars until light and fluffy. Beat in egg and vanilla. Add flour mixture; mix well. Divide dough in half. Shapre each half into a roll about 10 inches long and 1 1/2 inches in diameter. Wrap each roll in plastic wrap; chill at least 3 hours or overnight. Preheat oven to 400 degrees. Work with one roll of dough at a time, leaving remaining dough wrapped and refrigerated. With sharp knife, cut roll into 1/4-inch-thick slices. Place 1-inch apart on cookie sheets. Bake 8 to 10 minutes or until edges are light golden brown. Remove to wire rack; cool completely. Makes about 6 dozen cookies.