Preheat oven to 350 degrees. Place a baking sheet on center rack. Butter four 6-by-3-by-2-inch loaf pans, line with parchment, and butter parchment.
Mix flours, salt, baking powder, baking soda, and seeds. Cut butter into flour mixture with a pastry cutter or rub in with your fingers, until the mixture resembles coarse crumbs.
Whisk together yogurt, milk, honey, and eggs. Make a well in center of flour mixture, and pour in yogurt mixture. Stir well to combine (batter will be sticky). Spoon batter into pans, smoothing the tops. Scatter mixed seeds on top of batter.
Transfer pans to baking sheet, and bake until loaves are slightly cracked and golden brown, about 1 hour. (A skewer inserted into centers should come out clean.) Let cool in pans for 15 minutes. Turn out onto wire racks, and let stand for 2 hours.