I love citrus trees, and I had an extra Calamondin tree on my back porch in a 10-gallon pot. I didn't want to spend any money on a mail order tree or a bonsai tray, so I decided to 'bonsai' the calamondin and picked up a 6-inch plastic pot at Home Depot.
I severely pruned the tree (and incidentally removed all the leaf miner damage), and then pulled it out of its big pot. I wrapped the larger cuts with parafilm to keep moisture loss to a minimum. Once I got the tree out and exposed the roots, I pruned them in relative proportion to the top of the tree, and replanted it in the small 6-inch pot. I watered it in with rainwater, gave it a little Osmocote, and then placed it in the shed next to some Christmas lights (to keep it warm) for a few days.
I thought that if I had pruned the roots too severely I would see immediate evidence of distress, but the tough little tree didn't show any sign of trauma. I kept it moist for a few more days, and then brought it up to the office. My office is on the 5th floor of an office building downtown, where it is perpetually 72-ish degrees and 55% humidity. So far it seems to be doing just fine on my desk next to the window. Hopefully I'll see some new growth after it has had time to heal in.