In 1969, historian Paul Russell Cutright applied a nickname to Dr. Benjamin Rush's medicinal pills:

[A] product of the genius of Dr. Benjamin Rush, [the pills] were well-known in those days and alluded to, often with some feeling, as Rush's “thunderbolts.” Each consisted of 10 grains of calomel and 10 of jalap and consequently was a powerful physic.1

Calomel, derived from mercury, was a metallic substance with an alluring name. It was first manufactured in an alchemist's workshop in the fourteenth century.

In 1996, the thunderclapper nickname caught the attention of the general public with the publication of Stephen Ambrose's Undaunted Courage. “Those pills were under Dr. Rush's patent known as ‘Rush's pills’ but generally referred to as ‘Thunderclappers,’” intoned Ambrose in the text. This single addition to the Lewis and Clark lexicon galvanized historians and amateurs, and two years later in another publication, Ambrose amplified the description:

Rush's specific for nearly all the ills of mankind were purging pills composed of calomel, a mixture of six parts mercury to one part chlorine, and jalap. Each drug was a purgative of explosive power; the combination was so awesome the pills were called Rush's Thunderclappers.²

Neither Cutright nor Ambrose cited their source for Thunderbolts or Thunderclappers, and historians today use the terms with wild abandon, as if they were common names during the time of Lewis and Clark.³ David J. Peck, a physician and an author on the topic of wilderness medicine, stated that Lewis packed fifty dozen of Rush's pills known as “Thunderclappers” for the expedition, but did not list a citation for the term.⁴ One would assume that such a popular name would have an easily discoverable source in the secondary source literature since it is cited in multiple publications, yet there are almost no such references.

The first use of the term “Rush's Thunderbolts” was published in 1933 when Dr. Morris Fishbein described the pills in his book on the frontiers of American medicine:

A favorite prescription of the doctors of an earlier day in this country was Benjamin Rush's combination of ten grains of calomel and ten grains of jalap, given at a single dose as a strong purgative. It was known as Rush's thunderbolt.5

Rush's pills were actually another doctor's prescription. Dr. Benjamin Rush had learned of the pill from Dr. Thomas Young, senior surgeon in the military hospitals during the Revolutionary War. Rush modified Young's formula to fifteen grains of jalap and ten of calomel and prescribed it three times a day.⁶ He reported that “the effects of this powder, not only answered, but far exceeded my expectations.”⁷ In September 1793, he “imparted the prescription” to the College of Physicians as a cure for yellow fever, although today it is known that it has the power to cure nothing, and twentieth century medical textbooks discourage the internal use of calomel entirely.⁸

US patents for bilious pills were approved for several persons with the last name of Lee from 1796 through 1800. Benjamin Rush never filed a patent on a mercury pill or formula.⁹ However, there is some evidence on the etiology of a mercury thunderbolt or bolus in the annals of British naval medicine, but the author of the article describing it does not list a source for his information.

Treatment of all kinds of fever with large doses of mercury in the form of boluses of calomel was commonly practised by naval surgeons in the eighteenth century. They called it the ‘calomel plan’; their patients knew it as the ‘thunderbolt cure’ and the boluses as ‘thunderbolts’ because of the force with which they passed through the human body.¹⁰

A bolus is a “rounded mass, or a large pill,” usually applied internally.¹¹

To borrow a phrase from Mark Twain, this term is “the most majestic compound fracture of fact,” or as Dr. Thomas Szasz has stated, this “misattribution” is another “bogus Benjamin Rush quote,” which completely ignores and at the same time pokes fun at a frightful and archaic treatment in the dark ages of medical history.¹² The term cannot be traced back to Lewis's time through the secondary literature, nor have I seen a contemporary reference by Lewis or any other eighteenth- or early ninteenth-century person to “thunderbolts” in the primary source literature.