Chelidonius
Chelidonius is a stone which one finds in the stomach of a swallow. It is not very beautiful, but it surpasses all the beautiful stones in usefulness. It is of ten sorts and of two colors—black and red. The red is good for the frenzy which seizes people who are moon-struck; it restores their sanity to madmen and cures those who are pining away. He who carries this stone will be a good orator and will be much beloved. One must carry it wrapped in linen cloth and suspended under the left arm. The black, if worn in the same way, aids a man to accomplish important things he has undertaken; it is also a help against the threats and rages of kings and princes. The water in which it is washed is helpful to diseased eyes. If wrapped in linen cloth of saffron tint, it drives away fever and restrains the humors which injure the body.