The picnic table in the construction pictures is one without the corners under 45 degrees like in the first picture.
It is made completely of two by fours (89x38)
Step 1: The two benches
In total is have used 24 each 16 cm and have cut them when the table was ready.
Some coach bolt will even look better.
For the other connections i used wood screws of 80mm.
Click on "i" in the upper left corner of the pictures and than choose original file for a larger version of the picture.
A google sketchup version can be downloaded here
Step 3: Screw it all together
The horizontal connections are 50mm of the floor so it won't wobble on an uneven surface.