And then there are others.
Take the four engine Douglas DC-6.
This airplane has an arrangement whereby the center (inner) wing sections are bolted onto a wing box fuselage structure, then the outer wings (outboard of each outboard engine) are bolted onto the center wing sections.
A model of the DC-6 series, the DC-6B also has another distinction...it was the least expensive, by the measurement of costs per seat/mile, to operate than any other piston airliner.
Its remarkable engines are the primary reason...Pratt&Whitney R-2800CB16's.