Calculate mass held by rigidbody 2D

Hello, I have a "simple" question, is there any way to calculate how much weight a rigid body is holding?

 

Well, their is an option attached to the rigid body is called mass go check it out.

 

Yeah, well I know that every object has a mass, but how can you calculate how much muss is HELD by 1 rigid body.

Imagine you have a plane, and on top of this plane you have 30 more rigid bodies, how can you calculate how much mass that plane is holding?

 

Calculating the mass would be simple- just add 'em all up. It sounds like the real problem is how to figure out which objects are "held". Maybe you could use colliders for that.

 

Well not even that, because some objects could distribute some of their mass outside my target.

 

I think I found my solution, and I will be using reactionForce.magnitude of a spring joint