When looking at the actual fountain there is originality in the lines of the pool, the rocks, the vegetation, and the swans, offering certain liveliness. Rising from the foundation there is Mount Parnassus, the Muses, and the mythical Pegasus striking water from the rock. The water, in a single jet, creates a thin stream of water.
The anonymous author did not invent the ideas seen in the fountain; he simply copied it from the Jacopo della Porta fountain built in the 1600’s for the grounds of the Villa Aldobrandini. This was the famous “Hall of Winds” fountain which no longer exists. This is also where the artist of the sketch found the niche, covered by vegetation, as well as the arch covered in festoons, and finally the two smaller niches of the two standing female statues. There are still major differences between the two works. The della Porta composition features the figures lines up and sitting quietly in order. The anonymous sketch, however, is full of life and movement. The artist creates movement by making the muses rise in the pyramid moving the eye to Apollo, the most important figure. Each muse, herself, attracts the eye of the observer as she is fashioned in a lively position. The design is therefore the work of a great artist. It is in the architectural style of Bernini, and even logical to suggest that the style of the fountain is not just the likeness of Bernini, but actually by Bernini.
Now that Bernini’s name has been thrown out there, we must conclude that it was impossible for Bernini to have drawn this, or had it drawn for him, because of the horseman beside the pool. The style of the horseman, his clothing and is hair hanging down his back, as well as the tricorne hat, means that he cannot be any earlier than the first two or three decades of the 18th century. This fashion did not appear until 1720-30. Therefore, this sketch cannot be his, or it may be based on an original copy of a sketch by Bernini.