An out of the way sign that pairs with the one in Epic Jumps
Tutorial[]
At the 7th checkpoint (the one before the seesaw-like wooden beam), instead of crossing over the beam to the next checkpoint, use it as a catapult to launch you up and back. Your rider or bike should hit an afterburner at the bottom of the wall block acting as a roof above the 7th checkpoint. This is a hard one to hit, so it will take practice. To get an idea of where this afterburner is, when selecting the level from the track select list, watch the preview closely and you should see some of the afterburner sticking out from the other side of the roof. Fly up and a little forward to land in a section far up, but don't go too far forward when flying or you'll land on a trigger that activates a piston to push you back off.
Investigation[]
When combined with the secret found within Epic Jumps, the following is found.
_ED_V__APR___RT___E D__I _IN___OPO__ION_
DEDIVINAPROPORTIONE
DE DIVINA PROPORTIONE
This translates to "On the Divine Proportion" a manuscript by Luca Pacioli which concerns mathematical proportion and the golden ratio (which has shown up several other places).
Rhombicuboctahedron[]
The symbol with three circles and the number '4' on the sign are the Coxeter-dynkin diagram of a rhombicuboctahedron, one of thirteen Archimedian solids. This relates to the rest of the secret -- Leonardo da Vinci drew a rhombicuboctahedron for Pacioli's On the Divine Proportion. Included with the diagram is the inscription Vigintisex basium planus vacuus, which translates roughly to "Twenty-six flat empty faces" (which the rhombicuboctahedron has). Also, the page number, XXXVI (36) is given on the side.
Confirmation[]
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.