The Visio Tnugdali (Vision of Tundale) was the most influential vision of heaven and hell before Dante's Divina Commedia. It was written in Latin in the middle of the 12th century by a Frater Marcus in Regensburg and was soon widely circulated as well as translated into many European vernaculars.
The story tells of an Irish knight (Tnugdalus, later simplified Tundalus) who falls into catalepsis, but wakes again after three days of seeming death. He then tells how devils came to catch his soul, but an angel came to save him, showing him subsequently the terrors of purgatory and hell (it is disputed whether the text actually makes a difference between the two) as well as the pleasures of heaven. Tundalus' soul is then sent back into his body, to tell what he has seen.
The early manuscripts lack illuminations, but later artists were inspired by the detailed descriptions of the loci terribili where souls are being tortured.