Most early 19th-century writers looking to make multiples of their correspondence relied on the copying press. But that bulkier technology could not compete for portability with the “manifold writer,” like this one from Oxford’s Bodleian Library.
The first version of carbon paper was patented by Ralph Wedgwood—an estranged member of the famous Wedgwood pottery family—in 1806. The paper was the central component of Wedgwood’s “Manifold Stylographic Writer,” which was originally meant to aid the blind in writing (through the addition of thin metal wires to guide in forming words along lines), but was soon used primarily as a copying device. Wedgwood wasn’t the only manufacturer of manifold writers; the portable (approx. 8.5-by-10 inches) leather wallet above includes a label naming "inventor and patentee" F. Folsch.
To create a copy, you stacked (from top to bottom) a transparent sheet, double-sided carbon paper, and regular writing paper. You would then compose using a stylus; the pressure on the two-sided carbon paper transferred the text to the paper on the bottom, and produced a copy in reverse on the top sheet, which could be read because the paper was transparent. The “carbonated paper,” as Wedgwood called it, was made by soaking paper in a mixture of pigment and oil.
Wedgwood’s invention did not catch on quickly, largely because the method produced no “original” in ink, a standard requirement for much business correspondence. That said, it had early adopters – some of whom were more satisfied than others. Poet Robert Southey called it a “very excellent contrivance”; on the other hand, Thomas Jefferson wrote to Charles Willson Peale in 1807, noting with disapproval the olfactory effect of the oil used to create the carbonated paper: “The fetid smell of the copying paper would render a room pestiferous, if filled with presses of such papers.”
In the end, wide adoption of carbon paper came in the 1870s with the introduction of typewriting (and the development of better-smelling ink).
For more on Folsch, Wedgwood, and the early copying technology with the "pestiferous scent," see my longer post on the subject on the Bodleian Library’s blog.