A small polygonal virginal built by Franciscus Bonafinis in 1585 was ingeniously converted to a tangent piano in 1717; this was accomplished simply by replacing its jacks with shorter slips of wood and moving its strings so that they lie directly over the jack slots, producing an instrument with struck rather than plucked strings whose sound varies in loudness with the force applied to the keys. The instrument is now at the Metropolitan Museum.
Instruments employing this principle were well-known in the eighteenth century—the trend culminated in the Späth & Schmahl Tangentenflügel.
This according to “En route to the piano: A converted virginal” by Edwin M. Ripin (Metropolitan Museum journal XIII  pp. 79–86).
Above, the Museum’s depiction of the instrument; below, Michael Tsalka performs on a tangent piano.