[nine_k]

You are correct when you are talking about the origin of British patent law. There a king could grant a patent for a wide range of monopolies, including practicing a particular craft only by guild members, etc.

The US patent law, which I referred to, is not as old, and it definitely talked only about inventions, and explicitly required drawings, explanations, etc to be made available: [1]

[1]: https://en.wikisource.org/wiki/Page%3AUnited_States_Statutes...

[gdhbcc]

Given that american patent law was created originally as a copy of british patent law, through the statute of Anne, that distinction is irrelevant or even misleading.