Nelson Aldrich Rockefeller was a passionate collector of art of all kinds. He was especially responsive to sculpture, noting, "I'm interested in the strength, the vitality of it, the fact that you can touch it." His collection of modern art was extensive yet personal. In contrast, his method for assembling works of art from Africa, Oceania, and the Americas was highly systematic. From the beginning he focused on these works as fine art. This emphasis on aesthetic quality was the institutional criteria that defined the Museum of Primitive Art. The curator Douglas Newton noted that unlike other museums of the day that privileged ethnological or anthropological interests for their collecting, "We look for quality within each element—the best of everything."
Beginning in 1957 Robert Goldwater began providing Rockefeller with a steady stream of carefully considered memos regarding recommended purchases. Prior to sending these formal rationales for acquisitions, he reviewed these with René d'Harnoncourt. Among the most expansive of these was a proposal dated December 31, 1957, making the case for his acquisition of the Ivory Pendant Mask from the Court of Benin that is among the Metropolitan's most celebrated masterpieces. In his brief he argued for its superiority to the celebrated example in the British Museum: "I believe this mask surpasses it in delicacy of workmanship and penetration of expression. It is thus the best object of its kind known, nor will any others ever turn up." In arguing for its transformative importance to the MPA collection he compared it to what was then one of the most recognizable works in MoMA's collection, a painting by Henri Rousseau: "the purchase of this mask would give the Museum a permanent, primary attraction—a popular masterpiece. It is one of those objects that "has to be seen" by scholars, art lovers, and the public alike. As René has suggested, it is the kind of object that would . . . have to be put permanently on view; like the 'Sleeping Gypsy' of primitive art."
In 1958 the New York Times announced Nelson Rockefeller's acquisition of the Benin Ivory Pendant Mask for a record price. For Goldwater this singular acquisition came to "crystallize a policy." From this time forward he recommended that the MPA mission be that of "A Museum organized around permanent exhibition galleries where outstanding masterpieces of each area will be continuously accessible to the public, and other galleries with changing exhibitions."