A group of atheists tried to convince a Second Circuit panel Thursday that if a museum commemorating the Sept. 11, 2001 terrorist attacks displays a cross-shaped steel beam found in the wreckage of the World Trade Center, it should also be required to display a symbol recognizing atheists who were affected by 9/11.

At issue is whether the cross is a religious symbol or an historical artifact. American Atheists Inc. originally wanted to prevent the museum from displaying the cross at all, saying it would violate their constitutional rights.