Preheat oven to 350 degrees F.
Place bread cubes in a 1 1/2-quart buttered baking dish. In a saucepan, scald milk; let cool. In a bowl, beat eggs well; add scalded milk, sugar, salt, raisins (if desired), and vanilla.
Pour mixture onto bread cubes and combine lightly. Fill a second, larger baking dish with an inch or two of water, and place bread mixture dish inside.
Bake for 50 to 60 minutes, or until a knife inserted into the center comes out nearly clean. Serve warm.