C.A. Phillips’ Bosom-Pads, patented on February 18, 1873.
… ow.
Record Group 241: Records of the Patent and Trademark Office
Image description: Drawing of a pair of what we’d now call bra inserts. Each side is made of a stiff wire curved into a sort of cloverleaf shape to create a curved structure, with padding on the outside. Between the two pads is a cloth tape, presumably so the wearer can connect the pads to their undergarment.
Source: catalog.archives.gov