We found this interesting circuit that can be adapted to use integrated circuits and even microcontrollers in a Craft radio from 1942. The magazine can be downloaded from the link on page 40. The idea is to measure the RF absorption as shown in the graph. The circuit basically consists of an oscillator and a coil coupling system where the egg is placed. An interesting idea.
https://worldradiohistory.com/Archive-Radio-Craft/1940s/Radio-Craft-1942-10.pdf
