I was reading a good article from wetcanvas.com on compositional rules in landscape paintings and encountered one I don't understand and that has no explanation. The statement is that one should never start a visual path (like a river or road) from a corner. For context, it's the first rule on this page.
Why is starting a "visual path" from a corner detrimental to composition? I'm a bit confused and if someone could demonstrate with an example I'd be grateful.