Sprinkle yeast over warm water.
Mix together 1 cup flour, sugar, salt, margarine, and egg.
Beat into water-yeast mixture for 2 minutes.
Then add 2/3 cup flour, and beat for 1 minute.
Add raisins and rhubarb and beat until well mixed.
Spoon batter into greased muffin tins until they are 1/2 full.
Cover with a clean dish towel and put in warm place to rise (over hot water heater, for example) for 45 minutes.
When doubled in size, bake at 375° for 15 minutes.