Even with this clear statement about the Porter Fountain, when this document was discovered, it was preferred to believe that there was no fountain before the time of Pope Gregory XIII, noted at the time when public fountains began. The believed that this fountain was built, but was not used. Which is absurd, because the Aqua Vergine, the Trevi water aqueduct, was in good working condition before the time of Pope Gregory.
The argument stemmed from Albert Cassio who refuted the statement because the fountain was not listed among the works of Michelangelo written by Vasari. However the fountain is mentioned and linked to Michelangelo, by Vanvitelli, who was logging inventory, and had no reason to make it up, giving precise details and descriptions of the items created for the company of Jesus only, and not any individual. Basically, meaning this fountain is evidence of a minor work by Michelangelo. Michelangelo worked on the building where the fountain is housed and carved the tomb of its most illustrious family member, so why couldn’t the fountain be of his work as well?