There is a codex in the Corsini Library in Rome, there are many documents that are signed and dated by Bernini regarding the Fountain of the Moor. However there is one document that is not signed or dated, but is definitely written by Bernini. It discusses the cost of the creation of two tritons and four fish on a fountain. It has the exact cost for these sculptures, and what it will cost to move them to the location. The question is what project is Bernini quoting?
There is a beautiful water color by Bernini, in the royal library at Windsor, that shows an elaborate fountain with two Tritons holding up four fish (dolphins). There is another sketch of this fountain, kept in a collection of sketches by Bernini in Berlin, that these sketches were an actual plan for a real fountain. The conclusion is that after “the snail” was removed from the Fountain of the Moor, Bernini had designed a more extensive arrangement, more in his own style.
The assumption is that this plan also failed to please the pope, who did not want another layer to the fountain, making it seem overcrowded by Tritons. This is a possible reason for it never being created.
However there is an account from Pope Innocent from May 2, 1653. This note said he was finally pleased with the model for the Fountain of the Moor, the model of today’s fountain. The Pope has the Papal Treasurer set aside 500 scudi for the completion of the fountain, stating "Judging that for satisfactory ornamentation of the old fountain in Piazza Navona located beside the church of S. Giacomo de’ Spagnoli restored upon our instructions last year [1652], some other figure must be put in its center instead of that Snail which had been placed there, [such figure] by its height and girth to more nobly fit the surroundings…”.
The orders of the Pope were to create a statue that would look distinguished and be able to stand out in the fountain, in the midst of the Tritons. It becomes clear, that for Bernini to fulfill the orders for the Pope he would need to make his Tritons and fishes of gigantic proportions, making a figure far too large for the size of the basin. This becomes the real reason why these sketches ever came to fruition. So only two of these characters were created, and approved by the Pope.
The sculpture that was created, between 1653 and the following December in Bernini’s own home, features a muscular Triton standing on a shell, using all his might to keep a hold on a dolphin trying to get away. This arrangement is true to Bernini’s form, an energetic work. The detailing, from the tensed muscles of the Triton, to the suffocating dolphin with his eyes popping out of his head, as he tries to get free.