Equivalence Principle for Massive Bodies. I. Phenomenology

The experimentally measured equality of inertial mass (m₈) and gravitational mass (m₆) of a body indicates nothing about the m₆{m₈} ratio to the order of gravitational self-energy/total energy of the body. Experiments are discussed, using astronomical bodies, which measure m₆{m₈} to the order of the gravitational self-energy of the bodies. The configuration of the stable three-body problem of Lagrange is shown to be particularly sensitive to the possible difference m₆{m₈}-1 of the Sun.