Combine pecans and dry ingredients in a large mixing bowl, stirring well to blend. Add citron, if desired, 3 eggs, and butter; mix well.
Shape dough into two 12- inch-long rolls; wrap in waxed paper, and chill until firm.
Cut into 1/4-inch slices. Place 1 inch apart on lightly greased cookie sheets; brush tops of cookies with egg white. Bake at 350° for 10 to 12 minutes. Remove from cookie sheets, and cool on wire racks.