I mostly fly AS and AA - but when I do fly BA and CX, I notice the safety video talks about the brace position. (The CX video seems a little more dramatic on this.)

Now, it makes sense that on AS/AA flights we don't need to know about the brace position, because of __<insert your own humorous reason here>___... but it gets me thinking... what's the correct/proper brace position.

Using Google Image Search, I see a lot of different brace positions. Arms under your legs. Arms crossed resting on the seatback. Hands over your head and against the seatback. (But I know not to interlace - or you end up with broken fingers. Oh, and take off the ol' glasses.)

Which one is the best/most proper?