In Davison v. Commissioner, 2 Cir., 81 F.2d 16, 18 (1936), the court said: "It may well be that a renunciation of the power of appointment would for some purposes relate back to the date of the death of the original testator. But we cannot believe that a right to appoint which inhered in the donee of the power for six years before it was formally renounced and which, if exercised, would have terminated the charitable bequests in remainder, may, by applying the legal fiction of `relation,' be treated as though it had never existed. The practical certainty required in order to justify the deductions of bequests to charity under section 303 (a) (3) (of the Revenue Act of 1926) is not to be satisfied in such an unreal way."