Cream butter in a large mixing bowl; gradually add 1 1/4 cups sugar, beating well. Add eggs, one at a time, beating well after each addition.
Dissolve soda in buttermilk. Add buttermilk mixture and vanilla to creamed mixture, beating well. Combine flour, salt, and pecans; stir into creamed mixture. Chill.
Shape into 1-inch balls. Place 2 inches apart on lightly greased cookie sheets. Grease bottom of a glass; dip in sugar. Press each ball flat. Repeat procedure with remaining balls. Bake at 375° for 8 minutes or until lightly browned. Remove from cookie sheets, and cool on wire racks.