Displaying two tables side by side

How can you display two tables side by side? Example:
> select * from t1; a | b
---+--- 2 | 2 3 | 5 4 | 7 9 | 0
> select * from t2; c | d
---+--- 4 | 5 7 | 3 3 | 2 1 | 1 2 | 0

Intended output: a | b | c | d
---+---+---+--- 2 | 2 | 4 | 5 3 | 5 | 7 | 3 4 | 7 | 3 | 2 9 | 0 | 1 | 1   |   | 2 | 0

Each table has no keys (and no OIDs). Order is not important, but each 
row from each table needs to be displayed exactly once.

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dave