I've seen packages with polyurethane foam used to protect the contents. I imagine filling a box with the Great Stuff would be fairly expensive, but you might be able to find a cheaper source, especially if there is a plastic supply place near you.
Maybe wrap the wood with plastic (saran wrap, bubble wrap, or even old shopping bags?), stick it in the box, maybe keep it off the corners/sides with chunks of styrofoam, and then put in the polyurethane foam.
Might be hard to get it back out after that, so maybe put the foam in individual bags or something.