What was involved in performing an official kowtow to a Chinese emperor in ancient China?

In China, the kowtow-ee first had to sink to his knees and fall prostrate toward the emperor.

Knocking his head nine times on the floor, he could then either lie prostrate with hands on the ground or could sit more upright, but with his eyes and head lowered to the ground.

Either way, the emperor was never to be looked at.

In the Han Chinese culture, the kowtow is the highest sign of reverence, and was used to show respect for one’s elders, superiors, and the Emperor.

These days, it is still used for religious and cultural objects of worship, although its use in contemporary Chinese culture is waning.