Magnets and garlic: an enduring antipathy in early-modern science
tandfonline.com
tandfonline.com
Submission statement: I'd heard about this before, that in Medieval Europe garlic was thought to deactivate magnets (note: this is not the only variant of the "garlic effect", just one common one) until people actually finally started testing it in the 16th century, but I'd never really read more about it than mentions... anyway, this article discusses a bunch of the details. Note the "Who came up with the idea of the GE?" section I found fairly hard to follow, but it does discuss a number of the variants of the hypothesis...