Mix together the dry yeast, sugar, and 1/2 cup Masarepa. Pour in 1 cup warm water and stir to a smooth batter. Mix in the salt, the rest of the Masarepa and the masa harina, adding enough water to make a loose dough. At this point, the mixture will seem too thin to form into balls. Let the dough rest for at least five minutes. The dough should then be much firmer. Scoop out the dough by spoonfulls and roll into balls. Put the balls aside on a cutting board or cookie sheet. They will need to rise about 10 minutes before cooking. Meanwhile heat enough oil in a deep frier to cover the balls. To cook the doughnut holes, drop them individually into the hot oil. Stir them or shake the frier basket occaisonally until the balls are a rich brown color and the foaming of the oil has substantially subsided. Remove the doughnut holes from the oil. If coating them with sugar, immediatly put the balls in a large shallow-sided bowl and sprinkle generously with the sugar and cinnamon miture. Roll the balls around in the bowl so that they are coated all over.