Mix cornmeal and flours in a large bowl with the baking soda, salt, and raisins. Beat together liquids in a separate bowl. Vigorously blend liquids into dry ingredients with a wooden spoon, then pour into two well-greased or buttered one-pound coffee cans. Butter two 6" squares of foil and tie around the tops of the coffee cans with string. Place on a rack in a closely covered pot, pour 2" of water into the pot, and weight down the cover for a tight seal and steam for three hours. Do not open the pot until at least two hours have passed. Let cool 20 minutes before unmolding.