[ofalkaed]

The human scale is often the source of the square, the 1. The height of common chair seats such as most dining chairs is ~elbow to finger tip of the average adult male, effortless to measure on the workbench and it will get your chairs into the range people expect from such chairs. This height would often be the source of the square the chair would be designed around because it forms the most substantial part of a chair, the base.

Standard table height is stand up straight, let your arm hang straight down, make a fist, your knuckles are at table height. Works perfectly with chairs measured by elbow to finger tip and perfect for working at while standing when doing things like kneading bread or pushing a hand plane, puts the surface low enough that you can put your upper body into it and not just your arms.

A great many of things we interact with on a daily basis developed the standards we have today centuries before we had standards for measurement, back when calibrated measurement was academic and legal, impractical and abstract.