Stumbled across this while enjoying capslock_spn. potthead took it upon his/herself to take a rather lovely shot of Jensen/Dean's spinal column and ass and... calculate the equation for the curve to fit it. :D
Here it is in all its glory:
y= -(sin(x^(1.7/6+4)+(1/x)) + 10
Oh my god, guys. It's beautiful.
The Ackles Ass Equation