Forge version: 28.2.0
Botania version: r1.11-378

Note: this seems to only be possible on servers

Tossing an item on the ground (in the inventory, via Q) at the same time as it is filled with mana will cause you to drop the real one on the ground, while a ghost version of the item remains in your inventory. This is possible with a normal band of aura but is pretty much guaranteed if wearing full Terrasteel or wearing a greater band of aura.

Most mana using items don't seem to work with this ghost mana, but the Flugel Tiara still allows flight.

Demonstration:
https://www.youtube.com/watch?v=n9sFtrXrDcQ