Magma pistons and pump stacks are overkill if all you need is a few magma workshops.
All you need to do is make a small obsidian farm with a minecart stockpile in it. Fill it with empty magma safe mine carts (iron, steel, nickel, candy), and then flood it with 7/7 magma. Obsidianize it and then mine out the now safe to handle minecarts. Assign the full carts to a one stop route on a dumping track stop and voila, 2/7 magma anywhere you want in your fortress. The only dangerous part is making a safe obsidian farm, and breaching any magma pools. It takes at least 4/7 to run a magma workshop, so if you only have 1 magma safe mine cart then it will take multiple castings to get it running, but there is always a use for more obsidian.
This takes about 9 mechanisms with at least 1 being magma safe. 3 levers, and 3 bridges with one being magma safe. A magma safe door makes access easier.
Advantages of this method include only having to create 2 shafts down, one for water, and one for stairs, which saves on mining time, and allows the magma to be placed nearly anywhere on the map. Of course if you are gonna need a lot more magma then you better start working on a pump stack or a piston.
I would think that this was common knowledge, but if it isn't, then it is now.