Nyal Williams wrote:

When was water first sanctioned in contests? I read
somewhere in Soaring that some of the pilots at Marfa
back in the 60s were putting 'suspicious looking packages'
behind them on the spars. The inference was that they
might have been heavy metal and possibly illegal.
Weren't gliders once weighed at contests?

There were no design limitations for contest sailplanes until the
advent of the standard class. If memory serves, the first version of
the standard class rules said: no retractable wheel, no jettisonable
ballast. But then the manufacturers made wheels that barely emerged
from the fuselage, making for difficult take-offs and hazardous
out-landings, and pilots took lead shot, iron bars and the likes on
board to maximize the wing loading, making for high energy landings. So
the CIVV (now IGC) chose to allow retractable wheels and water ballast
in the interest of safety, instead of further complicating the rules.