The Romans were excellent at torture methods...

 

The actual palm couldn't hold the weight of your body.  The part if just beyond the wrist (or right next to the wrist) can, in fact, hold your body.  I'm sure they would use some rope...that way the bodies could be left there for days! 

 

During the slave revolt (think Sparticus) the Appian Way into Rome was lined on both sides with rotting bodies.  Those bodies were left there to literally just rot off!  It was also meant as a method to suppress any future slave revolts.

 

I find it interesting how Jesus died on the cross so, quickly.  I remember in my Roman Empire class we learned how sometimes people would suffocate for 12 hours or more or the soldiers wouldn't break your legs to just let you suffer, until your lungs collapsed.  There are reports of people (who obviously were strong enough) to literally suffer for a couple days before their lungs collapsed.  It was definitely a horrible way to die!