https://en.wikipedia.org/wiki/High_school_baseball_in_Japan#Sacred_.22Dirt_of_K.C5.8Dshien.22 said:
In the 1937 Summer Kōshien, Kumamoto Tech (Kumamoto) advanced to the championship game, but lost. After the game, Kumamoto Tech player Tetsuharu Kawakami grabbed a handful of dirt from the playing field of Kōshien Stadium and put it in his uniform pocket as a memento. Some years later, in the 1949 Summer Kōshien, after Kokura High (Fukuoka) lost to Kurashiki Tech (Okayama) in the semifinals, Kokura pitcher Kunio Fukushima scooped up some Kōshien dirt and took it home. This has become known as the original scooping of "the dirt of Kōshien" (甲子園の土 Kōshien no tsuchi). Since then, as a memento of their fleeting time on the hallowed grounds of Kōshien, players from the losing teams take home a pouch of the precious soil.
At the 1958 Summer Kōshien, Shuri High (Okinawa) became the first school to represent Okinawa (then under U.S. government rule) in a Kōshien tournament. They were eliminated in their first game by Tsuruga High (Fukui). After the game, they collected souvenirs of dirt and took them home. However, due to quarantine regulations of the Ryūkyū government they were not allowed to keep the dirt, and it was confiscated. Some Japan Airlines flight attendants heard about this, and had a sea stone lying outside Kōshien Stadium sent to Shuri. Even today this "Monument of Friendship" lies in the yard of the school as a reminder of the first trip to Kōshien by a team from Okinawa.