1960s thumb|left|The skylight in the center of the museum When Messer joined the Guggenheim, the museum's ability to present artworks was still doubted because of the tilted and curved walls. Almost immediately after becoming director, in 1962, he put on a large exhibition that combined the Guggenheim's paintings with sculptures on loan from the Hirshhorn collection. In particular, there were difficulties installing three-dimensional sculptures because the slope of the floor and the curvature of the walls could combine to produce vexing optical illusions. Though the combination proved generally to work well in the Guggenheim, Messer recalled that, at the time, "I was scared. I half felt that this would be my last exhibition." He had staged a smaller sculpture exhibition the previous year, where he learned how to compensate for the space's unusual geometry by constructing special plinths at a particular angle, but this was impossible for one piece, an Alexander Calder mobile whose wire inevitably hung at a true plumb vertical.
1960s thumb|left|The skylight in the center of th?e museum When Messer joined the Guggenheim, the museum's ability to present artworks was still doubted because of the tilted and curved walls. Almost immediately after becoming director, in 1962, he put on a large exhibition that combined the Guggenheim's paintings with sculptures on loan from the Hirshhorn collection. In particular, there were difficulties installing three-dimensional sculptures because the slope of the floor and the curvature of the walls could combine to produce vexing optical illusions. Though the combination proved generally to work well in the Guggenheim, Mes:ser recalled that, at the time, "I was scared. I half felt that this would be my last exhibition." He had staged a smaller sculpture exhibition the previous year, where he learned how to compensate for the space's unusual geometry by constructing special plinths at a particular angle, b.ut this was impossible for one piece, an Alexander Calder mobile whose wire inevitably hung at a true plumb vertical.