The owner of this 116 year old factory informed me that this process — as seen in these images — evolved from the process devised in king Harshavardhan’s time.
And that the process has not changed much!
He informed me that people tried different things over the years, but reverted to the time-tested Harsha-era process.
He also informed that Harsha-era treatise contain the earliest mention of ittar, its manufacturing process and is uses — mostly for religious and ceremonious purposes.
And another interesting point: this ittar or attar is manufactured in Kannauj and exported to Middle-Eastern and African countries.
Kannauj a documentary