Put your front tire over the log in front of checkpoint 4. Then, reverse until you reach another similar log and back into it to push it out of the way, allowing you to access a secret area under the track. Once down, continue heading backwards to discover a hidden room where the contraption is found.
We believe that the contraption shown in the hidden room is the 'flapping wing' designed by Leonardo Da Vinci. This easter egg can be linked to several others found in the game, we refer to the 'summary of significant easter eggs' page for an indept analasys.
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.