If you read about icons and the hand gestures (teaching, blessing, or however many there are) on Eastern Orthodox and Catholic sites they always write that two fingers together or two fingers up or something has something to do with the two natures thing. Is that just something they say today to explain it or does it have some historical base? Like, do we know for sure all the symbols behind the hand gesture in the Pantocrator in Mount Sinai for example?
For example this article: http://iconreader.wordpress.com/2011/05/26/what-does-this-hand-gesture-mean-in-icons/
The three fingers of Christ – as well as spelling out “I” and “X” – confess the Tri-unity of God: Father, Son and Holy Spirit. The touching finger and thumb of Jesus not only spell out “C”, but attest to the Incarnation: to the joining of divine and human natures found in the body of Jesus Christ.
This one for example (it's a Coptic one, from the Father Lazarus documentary):