We are studying math history with this book
Agnesi to Zeno: Over 100 Vignettes from the History of Math [Paperback]
Sanderson Smith (Author), Ellen Hayes (Illustrator)
The first chapter is about the origins of numbers. Maybe I will write up a blog post about that later.
The 2nd chapter is about Pi. I was extra nervous that Pi would be to complicated for my children. They loved learning about Pi, surprising enough. Though they only have a very basic understanding of it. Here are some of the fun things we used to learn Pi. The best was the Learning Upgrade Pi song, my kids are all singing that song now, though they do not know what it all means yet.... We will get to that though.