From Egyptian Secrets of Albertus Magnus, Joseph H. Peterson edition:
To make a Magnetic Compass which will serve to Discover the Treasures and Ores in the Bowels of the Earth.
For this purpose a magnet made of the plusquam perfection, accompanied by the prime material of which all metals grow is requisite: with this, the magnet of the compass must be strengthened. Around the compass are engraved the characteristic signs of all the seven metals. If it is desired now to ascertain what kind of a metal is most likely to be found in a hidden treasure or in ore beneath the earth, it will be only necessary to hie to that particular spot, where the magnetic rod has given the indication, but you must put your foot there where the perpendicular shows its attractions, and take of every metal a small piece, that is, one as heavy as the other, and lay it upon the resp. character and the needle will rotate to that metal which predominates under the surface of the earth, and there it will stand still.
Timeline of related events
1725Publication of Egyptian Secrets of Albertus Magnus (lists this spell)
1869English-language translation of Egyptian Secrets (lists this spell)