Here is an Ancient Roman Recipe for Garum:

Use fatty fish, for example, sardines, and a well-sealed (pitched) container with a 26-35 quart capacity. Add dried, aromatic herbs possessing a strong flavor, such as dill, coriander, fennel, celery, mint, oregano, and others, making a layer on the bottom of the container; then put down a layer of fish (if small, leave them whole, if large, use pieces) and over this, add a layer of salt two fingers high. Repeat these layers until the container is filled. Let it rest for seven days in the sun. Then mix the sauce daily for 20 days. After that, it becomes a liquid.

(From Gargilius Martialis, De medicina et de virtute herbarum)