The current AirPods panic isn't the first. Neither was the Sony Walkman. This piece focuses on what happened when audio became viably portable for the first time, in the 1950s and 1960s.

Dimensions and weight tended toward handheld and pocketable devicees. One early radio (Sanyo Electric 8S-P3) had dimensions of 150 x 80 x 45 mm / 5.9 x 3.1 x 1.8 inch <https://www.radiomuseum.org/r/sanyo_85_p3.html>. The Regency TR-1 measured 3" × 5" × 1.25" (7.62 × 12.7 × 3.2 cm) and weighed 12 oz (340g) <https://en.wikipedia.org/wiki/Regency_TR-1#Design>.

I suspect parallels might be drawn to pocketbook paperbacks (1935) or Pamphilus, seu de Amore (c. 1387), from which comes the word pamphlet, though limited literacy in the 14th century would likely have blunted impact.

Incidentally, the dimensions of the first Penguin Edition paperbacks, 6.5" by 4.25", would have about an 8" diagonal measurement (7.766", or just shy 20 cm). With a subsequent height increase to 7", the diagonal measure was about 8". <https://en.wikipedia.org/wiki/Paperback#The_early_years:_193...>

Most current smartphones fall into the 6-inch range: <https://www.whatismyscreensize.com/blog/mobile-screen-sizes>.