OK, in the name of science my 11 year old has just conducted the experiment. I didnt tell him why (in fear of him rolling around on the floor in laughter at me)
Small rectangle magnet suspended on cotton. This was then suspended over a distance so that he wasnt holding the cotton so not to interefere with results.
Tested on fertile quail eggs, eggs in incubator and day old quail chicks in brooder.
i can conclude that when tested on any of the eggs the magnet did not move at all in any direction, didnt even flicker.
But boy, when we put day old chicks underneath it was swinging and shaking like a good un ........... calm down, only because they were pecking it, other wise again it did not move.
Make of it what you will. Perhaps you need a certain amount of positive thoughts for it to work.
I remain sceptical and will carry on using my own method of sexing. If it lays an egg it's female if it crows it male.
I then told my 11 year old why we were doing it and he went around the house testing things and concluded the lounge carpet was female and the TV was male