The hathmic system, also known as the hathom-hecand-hemoth system, is a hexadecimal anthropocentric system of measurement, created as an exercise in recreational arithmetic, as an intellectual folly, and possibly for purposes of fiction. The names aren't serious, mostly just bad puns on various historical units (fathom, plethron, li, league, fist, watch, behemoth, and quadrans).
units are often more useful to humans than geocentric ones, but they
should be based on some consistent scale rather than using different
ratios between units. The metric system is inconvenient in
anthropocentric terms, but is very convenient in being based
consistently on a decimal system. But the decimal system is kind of
boring, so this system based upon hexadecimal comes from a made-up
culture that reveres squares. Different systems of measurement are good
at measuring different things; this system is focused on representing
human-scale walking travel times. For example, in one haach (of time), a
person can walk about one hleeg (of distance).
The base unit is the hathom,
which by astonishing coincidence is precisely 1.8 meters. This is six
feet in metric (25-mm) inches, or about 5 feet 10 inches, roughly the
average height of a human male. Sixteen hathoms are a lethron, which is 28.8 meters or about 94.5 feet. Sixteen lethrons are a hli, which is 460.8 meters or about 0.29 miles. Sixteen hlis are a hleeg, which is 7.372 kilometers, or about 4.58 miles.
Going smaller, one-sixteenth of a hathom is a lister,
which is 112.5 millimeters or about 4.43 inches. A lister is further
divided into sixteen units, each of which is each to about 7 millimeters
or 0.28 inches.
The most practical unit of time is the day, one-sixteenth of which is a haach. This is an hour and a half long. The base unit of time, however, is the hecand, which is about 1.3 seconds. There are 65,536 hecands in a day.
There has to be a base unit of mass, to fill out the system; I'm just ripping off SI on this. The base unit of mass is the hemoth, equivalent to 5,832 kilograms. More commonly, people would use a huad, which weighs about 89 grams. Sixteen huads weigh about 1.42 kilograms.