In this paper we will propose an empirical analysis of spatial and temporal boundaries. Unlike other proposals, which deal mainly with the commonsense level of the subject, we will ground our explication on well-established scientific practice and language. In this way we show how to reconsider in an innovative way questions such as the distinction between the bona fide boundaries and the fiat boundaries, the thickness and the ownership of the boundaries. At the same time we propose a division between (...) ex mensura boundaries and qui vulgo dicuntur boundaries. What is it, therefore,that divides the atmosphere from the water?[Leonardo da Vinci, Notebooks]. (shrink)