This was the first easter egg discovered and reported by the Trials community [thread]. It's simply a rectangle that seems to divide into smaller and smaller squares.
To get to this easter egg, start by going to the third checkpoint (on the logs). Drive up the log ramps, then carefully drive off the end of the top-most ramp so that you land on the log behind the flames, but in front of the dynamite box.
From here, reverse into the hole that has been opened up by the logs. You'll land on a platform below, from which you need to continue reversing. When you fall off of that platform, you'll land on a stack of tires and wood planks. The tires and platforms may be scattered or you might catapult the next platform in the air. If either of these happen, you may have to try again. Drive forward, go up the ramp, and you'll see that the metal wall in the background will fall away, revealing the set of wooden squares. Going forward from here will see you running into some explosives.
It is currently believed that the odd shape resembles the Fibonacci pattern. Looking at the Wikipedia article, you can see that the first image on the right appears to be identical to the pattern seen in the game. After doing a bit of reading on the subject, it becomes quickly evident that the rectangle is not dividing into smaller squares, but rather that the squares are multiplying in size to form a larger shape.
Also note the second pattern using the tiling to create a spiral. This image could be found in the De Divina Proportione, mentioned in Epic Jumps.
It was indicated in this article (http://www.redlynxgame.com/forum/viewtopic.php?f=28&t=5365&p=69159#p69159) that there was references in the game that relate to the arrangemen of leaves on a plant stem. It is understood that this reference was a clue to the fibbonacci patern found on this track. More details about this pattern occuring in nature can be found here:
This section is reserved for Confirmation/comments about this investigation. Investigations will remain open until advised by Redlynx that the final solution for each secret is found.