It is just an old convention for describing a box (box{max,min}).
And it seems to have been with us forever. But lets give this 
description a try: box { <4,0,4>,-4 }= a box that has
no size in this universe (max. is less then min) but might have
some volume in a non-POVian universe.

Sigmund Kyrre Aas wrote:
> 
> Not that it matters all that much..
> 
> Why do I get a surface here:
> 
> isosurface {
>   function {sqr(x)+sqr(z)-sqr(y)}
>   contained_by { box { -4,<4,0,4> } }
>   pigment {rgb y}
> }
> 
> but not here:
> 
> isosurface {
>   function {sqr(x)+sqr(z)-sqr(y)}
>   contained_by { box { <4,0,4>,-4 } }
>   pigment {rgb y}
> }

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