I have a cactus tree, pachipodium, I can test it out for you.
Only thing is the pot has a diameter of about 60cm, and the tree itself stands about 1.5m tall.
Not sure how to get it close to the monitor.
If you're not sure what it looks like, here is a link to a photo of a very pretty tree:
http://outdoors.webshots.com/photo/2620371540058336098iKKRct?vhost=outdoors
Dooh, I forgot, I use an LCD monitor, oh, bad luck on that one.
While on the subject of the cactus, my particular tree is now getting too big for its pot. It was manageable when smaller to plant over, now it's a different kettle of fish.
So me and my dad stood discussing it one day. Bet you would be interested in his suggestion of how to replant it.