Blend egg and sugars; add peanut butter and vanilla. Add rice flour (dough will be stiff). Mix in the water (add more if necessary, but one teaspoon at a time). Roll into 1-inch ball and place on an ungreased cookie sheet. Using a fork, press each one with a criss-cross. Bake in 350 degree oven for about 10 to 12 minutes. Let cool before removing from cookie sheet. Makes 2 to 2 1/2 dozen.