From NY Times Cooking:
1 ½ teaspoons whole coriander seed
1 ½ teaspoons whole cumin seed
1 ½ teaspoons black peppercorns
2 ¼ teaspoons coarse kosher salt
1 ½ teaspoons dry mustard powder
1 ½ teaspoons chile powder
3 tablespoons dark brown sugar
3 - 4lbs Boston Butt
Assemble the spice rub for the pork: In a dry, small skillet over medium-low heat, toast coriander, cumin and peppercorns until fragrant, 1 to 2 minutes. Using a spice grinder or mortar and pestle, grind toasted spices into a fine powder. Transfer to a bowl and mix with salt, mustard powder, chile powder and sugar.
If your roast is tied up, untie it. Massage meat generously with spice rub. If you have time, let meat rest for an hour or two at room temperature, or refrigerate for several hours or overnight.
Heat oven to 300 degrees. Place pork in a baking pan and roast for 3 to 4 hours or until meat is pull-apart tender and internal temperature reads 200 degrees on a meat thermometer. Let meat cool for at least 30 minutes before pulling it apart and shredding with your hands or two forks. (This works best when the meat is warm but not hot.)
Serve with your favorite BBQ sauce and coleslaw!