I completed a Masters in Mathematics back in 2014, involving a lot of historical research into the development of geometry. At the time, the ease with which I could open up books written over a century ago, search them and read them, was a fantastically useful tool.

I have some of those sources still on my hard drive in their scanned PDF format. They've now effectively vanished from the open internet. So much, available for such a short window. Our children will never believe us when we tell them what was once right there at our fingertips, and those that do should never forgive us.