Dissolve the yeast in the water in a large non-metal bowl. Let stand for 5 minutes.
Stir in the whole wheat flour, all-purpose flour, and salt until well blended.
Cover the bowl and place it in a warm location until the flour mixture has almost doubled. (See note.)
After the flour mixture has risen, combine the brown sugar, oil, maple syrup, soymilk, vanilla extract, baking powder, and baking soda in a small bowl. Mix thoroughly, breaking up any clumps of baking powder or baking soda.
Pour the sugar and oil mixture into the raised flour mixture and stir until well blended. Mixing with the handle end of a spoon or other thin item like chopsticks can make it easier to break up the long strands into smaller clumps. The batter does not need to be completely smooth, but you don’t want too many clumps larger than the last segment of your pinky finger. Let stand for 15 minutes.
Preheat the waffle iron for 3 to 5 minutes while the batter is standing.
Spray both grids of the waffle iron with oil. Pour or ladle the batter into the center of the iron, covering no more than two-thirds of the iron’s surface for the first waffle. Adjust the amount as needed for subsequent waffles.
Bake each waffle for 3 to 5 minutes, or until it can be removed easily. Spray additional oil on the grids prior to each waffle.