1. Noscere (to know):air:To gain knowledge; knowledge to do ritual magick. Ever hear the famous phrase "knowledge is power"? When you don't know enough about what you're doing terrible mistakes can be made. This is true not only in magick but in all aspects of life
2. Audere (to dare):water:To practice magick. Is the spell needed? Will it work? All sorts of questions go through the mind of the newest practitioners. I'll tell you a little secret, the same questions go through the minds of those who have practiced for decades as well. However, when practicing magick there is little room for dout. Dare yourself to do the spell and know it will work.
3: Velle (to will):fire:To will the manifestation. Just lighting some candles, burning some incense, and saying a few words isn't all that's needed for magick to work. You MUST will it as well. Feel it in your very being. Actually channel the energy. Not just say you are. It takes practice, but everyone eventually learns how to do this.
4: Tacere (to be silent):earth:Be silent about magickal workings or you may dissipate the energy you send out. Afterall, if after you do a spell you start talking about it to everyone you're not letting the energy from the magick be released to go do it's work.
There is a fifth power which you hear very little of. However, I feel that it is just as important as the rest.
5. Ire which is to progress or evolve and corresponds ot the Spirit. This is important not so much for magick but for the soul and is needed for both
All four of these ancient teachings are needed for magick to work properly. If any of these are missing the spell/magickal work most likely will fail.
While each one holds it's own level of importance, none of them are more important than the rest.
I haven't yet learned where the Four Powers of the Magus orriginated from. I wrote them a long time ago in my Book of Shadows and have heard them referred to by other practitioners. No one knows who orriginally wrote about them and I didn't write in my BOS where I orriginally heard them from.