"Visible Sound. I. Voice-Figures" appeared in The Century Illustrated Monthly Magazine, volume 42, at page 37. Watts Hughes describes finding the figures in 1885 while looking for a way to indicate the intensity of vocal sounds, and having since exhibited them in London at the Musical Association, the Royal Institution and the Royal Society.
The apparatus is described plainly enough to rebuild: soft sheet rubber stretched tightly over the mouth of a receiver, the voice introduced through a wide-mouthed tube, with the membrane sometimes stretched directly across the tube itself. She started with sand and lycopodium, then flooded the disc with a thin layer of water or milk, and noted that a note sung too forcibly throws the liquid up as spray too fast to follow — so she moved to denser, coloured liquids.
It is a first-person account of iterating a rig, published in a general magazine, and it reads better than most modern write-ups.