What is the difference between the basic structure of ancient and modern chairs?

In ancient times, the angle of the chair back was relatively upright, but in modern times, it has a certain inclination and radian, which is more humanized and comfortable. In ancient times, chairs were painted and carved on wood, but there are many modern materials, such as leather, chemical fiber, pure wood, cotton and linen. In ancient times, the legs of chairs mostly landed directly. In modern times, many of them were equipped with universal pulleys, and some of them were equipped with chair leg covers alone.