Elliott Waves A. Hamilton Bolton "hourly-close chart"

Hi everyone!
I’m going through the reading of the Elliott Wave principles.
Exactly at page 70, under the chapter “charting the waves” the books says as follows:
“A. Hamilton Bolton always kept an “hourly close” chart, i.e., one showing the end-of-hour prices, as do the authors”.
It then refers to it as a practical exercise "practitioners will find it instructive and useful to plot the hourly fluctuations of the DJIA.

What does it mean? I can’t seem to understand what this “hourly-chart” is and why should it come in useful?

Thanks in advance to anyone that helps me =)