Hours have always been 60 minutes. Minutes have always been 60 seconds. But the current definition of a second is the duration of 9,192,631,770 periods of the radiation corresponding to the transition between the two hyperfine levels of the ground state of the cesium 133 atom. I doubt that's how a second was measured 800 or 900 years ago.
And besides time, how were weights and measures standardized? I remember a documentary about the physical weights that all others are based off of. Like there was a small metal weight that was one ounce, and it was guarded in a room with other standard measurements. Is that generally how it has always been done? Or were weights and measures a lot less accurate historically?
They had standards but weren't very standardized. Before the metric system, different countries, regions and even towns had their own references for weight and measure. They could differ between commodities as well. (even now, gold is measured in troy ounces rather than imperial ounces)
See e.g. this table of some of the many values of the pound/libra - 460g in Amsterdam, 500g in Baden, 560g in Bavaria, 498 in Bremen, 499g in Denmark, 454g in England, 406g in Poland, 425g in Sweden, etc. And that's just during the 19th century when that was written, many places had changed their units over the years as well.
Yes, the old systems were usually based on some physical object as a standard.
