Even more basic, is the practice Alistair Crowley describes in Yoga as Asana, and is the first practice in the Liber MMM chapter, in Liber Null and PsychoNaut, as well as other places.
The idea is deceptively simple, but definitely not easy.
1) Position yourself in a posture that you can maintain for a long time.
2) Decide on a length of time to do the exercise for, maybe start with 5 minutes, and increase from there.
3) The exercise is to sit (assuming you chose a seated posture), in RELAXED SILENT STILLNESS for the duration. No talking, no excess tension, no adjusting posture, no wiggling, no facial expressions, no sounds, Swallowing is Ok as long its not obsessive or weird. Of course breathe naturally, but this is not about breathing, so don't do any special breathing thing, including focusing on it. The focus is to remain in present time. Do this with both eyes closed, for some sessions and eyes open for others. Decide in advance if this is eyes open or closed, then it stays that way until the end of the time. IF this time it's eyes open, blinking is Ok, as long as it's normal, minimal blinking every 10 to 30 or so seconds.
4) If you make a slight violation of these rules reset the timer and start over. At some point, probably less than 15 minutes this will become insanely hard. You will want to justify moving. Be smart, if there is a real world need to move, like you have to take a shit, do so, and restart. The goal is to be able to sit there perfectly still, relaxed, and quiet for 4 hours. This will take some time weeks and months to work up to. It is very hard. You may not be able to fully do it on your own. Most people can't. This is not meditation, it is being present.
If you have a cold, it will be very difficult.
Don't beat yourself up when you have to restart, just restart. It might take 100 hours to be able to consistently do 10 minutes well. It's time well spent.
Eat, drink water, sleep between sessions, and take good care of yourself in every way. Do not neglect any area that of life such as school, work, etc to do this. Things like tv, internet, other time wastes should be put aside so that you can find time to do this, if you choose to take the challenge.
If you wish read Yoga, Liber Null, etc. for some background. This trains your magical will.
Promise