At ground zero you will find a truncated cone at the ground. It's circular lid needs to be opened against the clock. Beneath you'll find a box, roughly shaped like a cube. Within there it is: the hexagonal prism.
It countains the sought for (cuboid) logbook. Unfortunately it is locked and will BREAK, not open if force is applied.|
So now you'll use the Powerbank you brought, as well as the USB-Cable (Type A to Type-B) you also brought. Most likely you will use the Smartphone with Internet as well. Supply power to the hexagonal prism and energy to your brain. Even if it's very convenient, please don't dangle the Powerbank on the cable but hold it together with the prism. As soon as you manage to change the circular LED from RED to GREEN, the prism will unlock and you can screw open the lid of the hexagonal prism. (Please don't try before the LED is green it will break, not open)
After logging, please place logbook and travelbugs (no other stuff please) back in the prism in a way that it does not block closing the lid back on. Please align the two marks on lid and edge as shown on the picture below:
Please make sure the power is still on and turn the hexagonal prism in a way that the numbers 3 and 9 face up one after the other as long as it takes to lock the box. Wait for the vibration confirmation for each nuber facing up. Repeat until the LED changes to RED and the hexagonal prism locks up. (If the Edges were not aligned as shown above, the hexagonal prism is now defective.
One could think that all the geometric hints in the text could help opening the hexagonal prism. That may be, but you should not overrate this. The solution to this riddle however is close and obvious.
We recommend to take the prism away from the hide in order to solve it, otherwise you might be faced with stupid questions asked my passing muggles walking their dogs. If you have no idea how to change the LED's light to green, take a walk. A short stroll around the area with open eyes could be a good idea to freshen up your thoughts. If that does not help, come back after dusk.
Some powerbanks like to switch themself off when the current consumption of the attached device is low. You will be able to notice this if the led in the prism switches off. Be quick or add a second load two a second port on your powerbank is available or try another powerbank.
The Powerbank usually has an USB-A Connector. You'll need a USB Cable to connect Type A to Type B: