Today we're waiting for an IKEA delivery that, according to their email, will be a 10x10x10 cm box weighing 14 kg.

So density-wise that has to contain berkelium, californium, protactinium, tantalum, uranium, gold, tungsten, plutonium, neptunium, rhenium, platinum, iridium, or osmium.

We're of course hoping for platinum, and really not for plutonium, because the critical mass is 11 kg...