Boneset
2 of the 7 encyclopedias on this shelf carry an entry for Boneset. Both are reproduced below, so you can see where they agree and where they differ.
Aiton's Encyclopedia (1910)
Important: Safety Warning This page prescribes plants as medicine according to pre-modern medical theory. Several of the plants named are toxic, correct identification is difficult, and the doses given have no scientific basis. Do not ingest or apply any preparation described here. This information has been left in for historical purposes but should not be acted upon. or Thoroughwort, a stout, hairy, strong-scented herb. A member of the composite family closely related to Joe Pye weed. Boneset is a flat-topped plant about two feet high, with white flowers. It grows in moist meadows, copse edges, or old pastures and may be known by the lanceolate, warty, finely-toothed opposite leaves, so united at the base that they seem like one leaf with the stalk of the plant growing up through the middle of it. A bunch of dried boneset for an all around spring medicine used to hang in every well ordered attic. Boneset was in evidence if occasion arose at any time; but regularly in March or April it was customary to steep a jar full of the bitter stuff, of which each member of the family, well or ill, was invited, exhorted, urged, and required to partake freely "to clear his blood." See Pennyroyal; Medicine 2026 Editor's Note: The name is a clue to its old use: boneset was the standard American home remedy for the agonizing fevers called "break-bone fever" — dengue — and it was in nearly every farmhouse the entry describes. Modern analysis has dampened enthusiasm: the plant and its relatives contain alkaloids that can damage the liver, so the all-around spring tonic is no longer recommended. (Ed: BR 2026-06-11)
Collier's New Encyclopedia (1921)
or THOROUGHWORT (cupatorium perfoliātum), a useful annual plant, natural order compositæ, indigenous to the United States, and easily recognized by its tall stem, 4 or 5 feet in height, passing through the middle of a large, double, hairy leaf, and surmounted by a broad, flat head of light purple flowers. It is much used as a domestic medicine in the form of an infusion, having tonic and diaphoretic properties.