From an item in the National last summer:
Dr Raymond Murray said the first investigative use of soil analysis by the US Federal Bureau of Investigation was in 1935. But if there is truth in the legend, the FBI was preceded by quite a few centuries by the ancient Romans, who used to look at the soil under enemies’ horses in an attempt to guess at their previous whereabouts. […]
I have been unable to recall/find any mention of Roman soil analysis … anyone have any ideas?