Imponderabilia means which is not weighable, i.e. the substances which have no perceptible weights, they are immaterial power or energy; may be natural or artificial.

Medicines prepared from energy, available from natural and physical reactions are called imponderabilia.

Hahnemann observes in his Organon, aphorism 280, Footnote that, “even imponderable agencies can produce most violent effects upon man.” Dr. H. W. Allen describes their mode of preparations and symptoms in his ‘Materia Medica of Nosodes‘. Elizabeth Wright mentions six such sources of drugs in his book ‘A Brief Study Course in Homeopathy‘. Dr. Caspari, Jhar, Clarke, Swan and John Butler etc have described their symptoms.

Examples are:

1. Luna [ Full Moon ], Magnetis Poli Ambo [ Magnet ], Magnetis. Polus Australia [ South-pole of magnet ], Radium, Sol [ Sun's ray ].
2. Artificial – Magnetis Artificialis; X-Ray; Electricitus.