I assume it is a Lemma, that it is the invention of the machine itself, which is to give a patent right, and not the application of it to any particular purpose, of which it is susceptible. If one person invents a knife convenient for pointing our pens, another cannot have a patent right for the same knife to point our pencils. A compass was invented for navigating the sea; another could not have a patent right for using it to survey land. A machine for threshingwheathas been invented in Scotland; a second person cannot get a patent right for the same machine to threshoats,a thirdrye, a fourthpeas, a fifthclover, &c.
Thomas Jefferson, letter to Isaac McPherson, August 13, 1813
As sensible as this is, patents for applications is something drug companies are allowed to apply for, and use to keep generics off the market.