Recently Pottermore added a new exclusive content entry on Floo Powder to the second book, Harry Potter and the Chamber of Secrets. The content can be unlocked by clicking on the fireplace in Chapter 4, Moment 2.
Here’s an excerpt from the piece:
Floo powder was invented by Ignatia Wildsmith in the thirteenth century. Its manufacture is strictly controlled. The only licensed producer in Britain is Floo-Pow, a company whose Headquarters is in Diagon Alley, and who never answer their front door.
No shortage of Floo powder has ever been reported, nor does anybody know anyone who makes it. Its price has remained constant for one hundred years: two Sickles a scoop. Every wizard household carries a stock of Floo powder, usually conveniently located in a box or vase on the mantelpiece.
The entry goes on to explain incidences with wizards attempting to make their own Floo Powder, which is quite funny.
It’s worth a read so go and unlock it! Click here to read it immediately.