Sources : Rutela

Aristotle [ca. 350 BCE] (De animalibus, Book 8, 6.3): ...serpents can live a long while without food, this may be seen in those that are kept by dealers in medicine. - [Cresswell translation, 1887]

Thomas of Cantimpré [circa 1200-1272 CE] (Liber de natura rerum, Serpents 8.28): Rutela is a serpent of the East, created to be useful for many remedies, as abarenon says. This type of snake is caught by the storekeepers and kept in a safe place. In which it is to be noted that it lives for a long time without any food. But every kind of snake can live a long time without food, but especially the rutela. - [Badke translation/paraphrase]