NSF certifies drinking water filters to standards applicable to each type of treatment option. You may notice the NSF mark on a product along with numbers such as NSF/ANSI 53 or NSF/ANSI 42, which refer to the standard to which the filter has been certified.
The definition of a canon is a principle, law or standard by which people are judged or a member of the clergy living according to these principles or laws. An example of a canon is a moral principle that a group believes is correct or proper.
Polykleitos created his method around 450 BCE and called it âThe Canonâ coming from the Greek word kanon meaning measure, rule, or law. To prove his theory, Polykleitos created a heroic bronze statue of Achilles. Sadly, this statue was destroyed but since it was so widely known, many sculptors redid it.