Sparklines are not bar graphs, they're lines, hence the name. If you have a copy of Tufte*, you can find them on page 171.

Tufte has written up a history here: https://www.edwardtufte.com/notebook/sparklines-history-by-t...

This tool doesn't really create sparklines, but it does create small charts, although given it is delivered via custom font, it's usefulness is limited.

* And anyone interested in displaying information is doing themselves a disservice without a copy of "The Visual Display of Quantitative Information" by Tufte.