As much as I like the idea of floating the chunk of wall out with mercury I think there are at least two car related problems with the idea. One, if it fully filled the trunk it would weigh about 12000 lbs. Two, it would cause any aluminum car parts that it came into contact with to corrode rapidly. But it would be fun to watch 
You lost me!!!
I guess I have to start listening to all those reruns on Saturdays.
Yosemite
A guy in Germany borrowed his Dad’s BMW to transport a chunk of the Berlin Wall. The block just fit into the trunk, which made it impossible to get under it to remove said block.
This call hasn’t aired on Car Talk recently, at least not in my area. The OP must have been listening to either a satellite radio repeat, or sometimes a local fundraising NPR station will – instead of the regular weekly show – broadcast a specialized Car Talk produced just for the fundraiser period.
Berlin Wall…well, that was a while ago.
Don’t know what the chumps suggested, but I would have suggested taking several carabiners and JB Weld-ing them to the chunk to use as lifting points. JB Weld has a tensile strength of 3000 psi, so one square inch of contact area would be enough to lift whatever they could fit in a BMW trunk.