"Convenient carry container for your foci." -Azanor
In Thaumcraft, there are many wand foci. It can become very annoying and take up a large amount of space to carry 10 or so foci around you at which is why you discovered (not invented) the focus Pouch.
A Focus Pouch can be crafted at an arcane workbench using 10 perditio, ordo and terra vis.
"Once you have gathered a sizable collection of foci, it is quite annoying to carry them all with you. This pouch solves that problem.
Whenever you change the focus on your wand, it will check this pouch first and any foci that get removed will be placed inside it first. You can also right-click the pouch to place or remove foci by hand.
It can also be carried in your belt bauble slot."