the river Lethe

From another list:


Dear all--


I have recently come across, in a 15th century Latin poem, a reference to an unnamed hero who was made both invulnerable and immune to poisons by being dragged through the river Lethe. The usual version of the myth is that Achilles' mum held him by the heel to dip him into the Styx and make him invulnerable. Has my poet just made a mistake? Or is there another hero who comes from the Lethe instead?


If there is such a myth, is there a Latin version of it? For I assume that my 15th century poet had no Greek, though he could have done, I suppose. And this question is unfair, for it is seeking among medievalists information better sought among classicists. But I don't belong to a classical weblist, alas.


Many thanks for any help you can give.


Larry Eldredge