Before Jenny - Ernst Chladni, Robert Hooke, Galileo Galilei
In fact Jenny is just one in a long line of venerated scientist / philosophers involved with Cymatics, stretching all the way back to the original Father of Science Galileo.
Galileo was the first to notice the formation of regular patterns on an oscillating body while
experimenting with plates & chisels in 1632.
''....scraping a brass plate with a sharp iron chisel in order to remove some spots from it and running the chisel rather rapidly over it, I once or twice, during many strokes, heard the plate emit a rather strong and clear whistling sound: on looking at the plate more carefully
I noticed a long row of fine streaks parallel and equidistant from one another.." - Galileo
1680 : Royal society member, philosopher, architect and polymath Robert Hooke also noticed nodal patterns forming as he ran a violin bow along the edge of a glass plate covered with a fine layer of flour. Hooke is better known for giving us his law of elasticity [Hooke's Law] than for popularizing Cymatics.
it wasn't until Ernst Chladni later repeated Hookes experiments, publishing his findings
in the book Discoveries in the Theory of sound  that Cymatics began to reach
a wider audience.
Chladnis book describes how sand sprinkled on a plate could be excited by drawing a bow along the plates edge. When the bowed plate reached resonance the sand formed a pattern showing the nodal regions, almost exactly the same experiment that Galileo and Hooke had carried out many years previously. Because of Chladni's book however, his became the name most associated with the vibrating plate phenomena now known as the Chladni Plate
Variations on the Chladni plate [Chaldni modes] are still in use today by many instrument manufacturers. Most typically used in the design and build of guitars, violins and Cellos Chladni modes help to visually reveal how the body of an instrument is resonating at a given frequency, identifying potential problems during the instruments construction.
Chladni Modes on a guitar body