Arnold did this exercise by piling multiple sweaty men onto his back. But he's Arnold, and Arnold could get away with that. Here's a less-weird looking way to do this classic calf builder, no sweaty dudes or specialized machines required.
Strap on a loaded dipping belt and stand on a block or whatever you have handy, toes on the edge. Bend at the waist and do calf raises. You can perform them bilaterally (both legs) or unilaterally (one leg at a time). Hold the bottom stretched position for two seconds and hold the top position for at least one second, contracting hard.
If you haven't tried this one in a while, get ready for some intense soreness, regardless of how many standing and seated calf raises you've been doing.