In a large skillet, heat 1 1/2 inches water to boiling. Add salt and the 1/2 tablespoon rice wine vinegar. Break one of the eggs into a small bowl and gently slip the egg into the boiling water. Repeat with a second egg. Cook the eggs 3 to 5 minutes or until the white has set and the yolk has filmed over. With a slotted spoon, remove eggs to large plate. Repeat to cook remaining two eggs.
To serve, toss the spinach, arugula, olive oil, and remaining 2 tablespoons rice wine vinegar in a large bowl. Divide mixture among four serving plates. Top each with pecans, a sprinkle of red onion, the prosciutto strips, and finally an egg. Serve promptly.