Lyngurium

Also false are the statements made simultaneously about its medical properties, to the effect that when it is taken in liquid it breaks up stones in the bladder, and that it relieves jaundice if it is swallowed in wine or even looked at".

[8] This idea was apparently also mentioned by Theophrastus in a different, lost, work On creatures said to be grudging, and was still alive in the 15th century: "she hidith it for envy that hire vertues shulde not helpe vs".

[9] Another version was that the lynx swallowed the stone and "withholt in his throte wel depe that the grete vertues there-of ne shulde nought be helpyng to vs" ("withholds it in his throat knowing that the virtues thereof should not be helping us").

[11] The 11th century Islamic scientist Abū Rayḥān al-Bīrūnī was critical of a popular belief, not mentioned in other sources, that the stone could make people change gender.

[15] The death of belief in lyngurium generated a few attempts to find more scientific explanations, and a considerable amount of scholarly squabbling, but the absence of physical specimens was soon fatal.