Although Brancusi hardly courted controversy, he was at the center of two of modern art's most notorious scandals: the U.S. Customs office's refusal in 1926 to classify Bird in Space as a work of art, and the removal of Princess X from the Salon de Indépendants in 1920 on grounds of obscenity. Brancusi's friends and colleagues signed a manifesto, published in Le Journal du Peuple (February 25, 1920) to protest the authorities' decision. It was reportedly Picasso (although some accounts cite Matisse) who first had declared the work a phallus. Brancusi was infuriated by the comparison. He insisted the sculpture was a portrayal of a feminine ideal and denied alternate readings that characterized it as a sign of his desire for its model or a formulation of sexual duality.

Brancusi's hundreds of photographs of his work and studio present multiple views of most of his sculptures. Virtually without exception, however, Princess X is shown from the left front. From this angle, the two breasts are fully visible, the form is vertical rather than a rounded C, and indeed, the sculpture's eroticism is at its clearest. These photographs also emphasize the reflective properties of polished bronze, uniting the qualities of woman and mirror described in the title of the sculpture's original form (see Princess X, Sheldon Memorial Art Gallery, University of Nebraska). Ann Temkin, from Constantin Brancusi 1876-1957 (1995), p.140.