Petrache Poenaru's fountain pen: a mystery solved

A few years ago, I noticed that a number of online reference sites had quietly been updated with the claim that the first fountain pen (or, sometimes, the first cartridge fountain pen) had been invented in the 1820s by Romanian polymath Petrache Poenaru. It was not easy to figure out exactly what sort of pen Poenaru had invented, so I threw the question out here.

It took three years, nearly to the day, but now we have the answer, thanks to Simone Piccardi, who has posted a copy of the French patent here, with transcription.

The description, translated into English, is as follows (my translation, quick and dirty):

Explanation of the diagrams on Plate 1 which depict the pen assembled and in its details (the same letters denote the same parts in the different diagrams).
Fig. 1 shows the pen closed up in its case and ready to be placed in the pocket like a pencil. It consists of a tube A taken from an ordinary large swan quill of the sort used for making paintbrushes intended for map notes. At the end of this quill tube is fitted a little tube B in thin metal, whose end is threaded on its exterior, and which screws into a cap C, closed on top. The lower end of the tube A is fitted into the upper part of a little tube of thin metal shown in Fig. 2, which has three different diameters D, E, F. The upper part D receives, as we will explain, the lower end of the quill tube A, the lower diameter [step] E is a friction fit with the goose quill G, which is cut like an ordinary quill pen and which can be replaced as desired either by a quill of the same nature or by a metal nib. The middle diameter [step] E is a friction fit, a bit tight, with the end of the cap H, in metal, which covers the quill point G when one no longer wishes to write. At the bottom of this cap is soldered the base of a long needle I whose point, when one caps the nib after having written, goes into the end of the quill G and fits into a little hole of the same diameter as the needle's point drilled in the center of the base of the little end of tube F, to stop the ink from escaping.

In this fountain pen [plume sans fin], the quill tube serves as the reservoir, into which the ink is introduced through the end of the quill, all that is necessary is to unscrew the little cap C.

The advantages of this pen over those already existing for the same purpose, being that the tube A is of quill rather than of metal or glass, the instrument is by this means much lighter, less breakable, and to make the ink arrive at the point of the nib, it is not necessary to shake the pen, which is very inconvenient, all that is required is simply to squeeze the tube A with the fingers and the ink will in this manner be made to flow in greater quantity through the little hole drilled in the center of the base of the little holder F, fig. 2. This method also remediates any problems arising from temperature differences between the metals.

Poenaru's pen was not a cartridge pen, and the description clearly states that it was intended to be an improvement on existing fountain pens. Its distinguishing feature was a barrel made from a swan quill.