Former Citigroup Chairman & CEO Sanford I. Weill, the man who invented the financial supermarket, called for the breakup of big banks in an interview on CNBC Wednesday. What we should probably do is go and split up investment banking from banking, have banks be deposit takers, have banks make commercial loans and real estate loans, have banks do something that's not going to risk the taxpayer dollars, that's not too big to fail," Weill told CNBC's "Squawk Box." He added: "If they want to hedge what they're doing with their investments, let them do it in a way that's going to be mark-to-market so they're never going to be hit." He essentially called for the return of the Glass-Steagall Act, which imposed banking reforms that split banks from other financial institutions such as insurance companies. He said banks should be split off entirely from investment banks, and they should operate with a leverage ratio of 12 times to 15 times of what they have on their balance sheets. Banks should also be completely transparent, Weill said, with everything on balance sheet. "There should be no such thing as off balance sheet," he said.