Pareus: natural to integral nature, and to the whole man, not to the body in itself
Pareus distinguishes between nature unfallen and nature corrupted. He says that with respect to unfallen nature Adam's immortality was natural, but that with respect to corrupted nature it is not immortality but mortality, that is, the necessity of dying, that is rightly called natural.
He also distinguishes between unfallen man and man's body considered in itself, and holds that immortality was natural to the man, not to the body in itself (on Bellarmine, On the Grace of the First Man, chapter 9). In chapter 5 he teaches that whatever belonged of itself to the principles of nature for its perfection, and without which nature was not first made in its principles, was natural to unfallen man.
Latin
XXV. Pareus vero distinguit inter naturam integram & naturam corruptam. Et dicit Adami immortalitatem, respectu naturae integrae fuisse naturalem: respectu vero naturae corruptae, non immortalitatem, sed mortalitatem, quae est moriendi necessitas, naturalem recte dici. Ac praeterea distinguit inter hominem integrum, & corpus ejus in se consideratum. Et homini, non corpori in se, immortalitatem naturalem fuisse asserit, in caput nonum Bellarmini de gratia primi hominis. Capite vero quinto homini integro docet naturale fuisse quicquid principiis naturae, ad ejus perfectionem per se adjacebat; & sine quo natura in suis principiis non erat primitus condita.