Basic Sourdough Starter - cooking recipe

Ingredients

1/2 pkg. dry yeast (1 1/4 tsp.)
2 c. sifted flour
2 tsp. sugar
2 1/2 c. water

Preparation

Feed me (sourdough) every Wednesday and Saturday or I will die. Do not use me the same day you feed me.
Take out what is needed before feeding.
Never let the dough get down to less than one cup.