From
thevintagenews.com
According to legend, the famous Soviet cosmonaut Yuri Gagarin had to relieve himself, just as he disembarked the bus that was taking him to the launch ramp. In the absence of a better solution, he simply urinated on the bus’ tire, unknowingly starting a tradition that would outlive him and become a necessary ritual among all other Soviet space-dwellers before their missions.
From that day forward, there allegedly hasn’t been a single space mission both during the Soviet Union and the current Russian Federation that has skipped this custom.