Preheat oven to 400°.
Pierce potato several times with a fork; place on a foil-lined baking sheet. Bake at 400° for 40 minutes or until tender. Cool. Peel potato; mash. Combine potato, cheese, 1/4 teaspoon salt, cinnamon, and nutmeg in a small bowl.
Working with 1 wonton wrapper at a time (cover remaining wrappers with a damp towel to keep them from drying), spoon 1 tablespoon potato mixture into center of each wrapper. Brush edges of dough with egg white; bring 2 opposite corners to center. Press edges together to seal, forming a triangle. Repeat procedure with remaining wonton wrappers, potato filling, and egg white.
Bring 6 quarts water to a boil. Add 8 ravioli; cook 2 minutes or until done. Remove ravioli from pan with a slotted spoon. Lightly coat cooked wontons with cooking spray; keep warm. Repeat procedure with remaining ravioli.
Melt butter in a small skillet over high heat. Add chopped sage to pan; cook 1 minute or until butter is lightly browned. Stir in remaining 1/4 teaspoon salt, juice, and pepper. Drizzle butter mixture over ravioli. Garnish with sage sprigs, if desired.