Sources : Indian Stone

Physiologus [ca. 4th century CE]: There is a stone called sindicus which has the following nature: if a man is dropsical, the doctors seek out this stone, and when they find it, they tie it to the dropsical man for three hours, whereupon the foulness leaves him and is absorbed into the stone itself. When they have untied the stone from the man, they weigh them both and the moderate-sized stone outweighs the man in the scales. If it is exposed to the sun for three hours, however, the stone pours forth the most foul water, which it received from the dropsical man, and becomes clean again just as it was before. - [Curley translation]