Escher prints
The impossibility I always liked was the demand to have an extremely large spreadsheets or building plans, printed on a single sheet of A4 large enough to read.
Multiple A4 sheets not acceptable,
A3 sheet still not legible enough
A2 Plan printer sheet legible but too big.
Some people just couldn't get it into their stupid litigious heads that it was impossible
Biting the hand that feeds IT
