 Celsus cites an opinion of Cato concerning the intercalary month, and the "regula" or "sententia Catoniana" is frequently mentioned in the "Digest".The "regula Catoniana" was a celebrated rule of Roman law to the effect, that a legacy should never be valid unless it would have been valid if the testator had died immediately after he had made his will.This rule (which had several exceptions) was a particular case of a more general maxim