A case in point—New Age embrace of the long-discredited Doctrine of Signatures.
The Doctrine of Signatures dates from the time of Dioscurides (c. 40 – 90 AD) and Galen (AD 129 – c. 200/c. 216). According to proponents of the doctrine, herbalists could use the vague resemblance between the appearance of herbs and body parts to treat ailments attributed, often wrongly, to those organs. The later Christian theological justification was that God would have wanted to direct men to useful plants.
Eyebright, used for eye infections
Hedge woundwort, thought to have antiseptic qualities
Liverwort, either Marchantiophyta or Hepatica - used to treat the liver
Lungwort – Lobelia pulmonaria (and others) - used for pulmonary infections
Spleenwort, Asplenium - used to treat the spleen
Toothwort, Dentaria - used for tooth ailments
In its innocuous form, this belief is embodied in the naming—both popular and Linnaean—of plants.
Unfortunately, because the doctrine has no basis in fact, the practice has proved invariably ineffective, often harmful, and too often fatal.
Examples (discussed in the playlist below):
Hyoscyamus niger, black henbane, for toothacheAristolochia clematitis, birthwort, in midwifery
Mandragora officinarum, mandrake, as aphrodisiac