It depends on many variables.
For example, genetics, especially on mitochondria, ATP, adrenergic system and metabolism in geral. Also, how you developed since childhood (how much weight and muscle you have build up).
When measuring, you should take in consideration if the person had the right nutrition, hydratation, enough sleep and even the purity of the air.
All of that just to measure how much someone can lift? So:
>It seems no one can answer this.
No one can answer because it's not important.

Get the right genetics, right nutrition/sleep, right exercises, plus some drugs (androgenic modulators, dopamine and (nor)epinephrine agonists) and you'll have a person with "high potential".
>constraints of the mind
This "limits are just on your mind" is all bullshit.