Creating a zoom button to increase text from 10 pts to 72 pts

Hello,

A couple of weeks ago, I saw a great example of how one could design for visual impairment by using a hotspot and developing a zoom button.  The author showed that when designing for accessibility one could click on this zoom button and the text would increase from 10 pts to 72 pts.  I have looked all over the internet for this example for weeks  and I can't find it.  Has anyone seen this example?  Can you provide the link?