Analysis of information sources in references of the Wikipedia article "Nature printing" in English language version.
The [leaf printing] technique was not well known at the time, although the Philadelphia naturalist Joseph Breintnall made contact nature prints from leaves about 1730.
Franklin probably got the idea of printing images of leaves on paper money from making these nature prints, which he and Breintnall sent to English naturalists. They were printed directly from inked leaves, which were placed inside a folded sheet of paper and run through the press.
In 1737 Franklin invented the art of nature printing from leaf casts, using a copper plate press, for transferring a sage leaf image onto the back of paper money bills, a technique intended to thwart counterfeiters.
Franklin probably got the idea of printing images of leaves on paper money from making these nature prints, which he and Breintnall sent to English naturalists. They were printed directly from inked leaves, which were placed inside a folded sheet of paper and run through the press.
