From the article:
Ruben van der Vleuten wanted to see what happened behind the scenes at the post office-so he outfitted a cardboard box with a (semi-legal?) camera and documented the trek.
He used a handmade rig equipped with motion sensors to capture video during movement, and used a separate battery to power the entire device. Even then, the footage you see is pieced together from multiple trips, sequenced together for an end-to-end view.
My personal favorite? The intense system of slides and sorting lines that the package is pushed through automatically.