Mermaid timeline box size

What I’m trying to do

I’d like to increase the size or width of mermaid timeline boxes. I’ve been using mermaid in canvas which has allowed me to make nice wide diagrams, but I don’t know how to change the size of the boxes. I can change the text size, but I can’t make more room for the text.

Things I have tried

Looked around for the applicable css to no avail. I’ve found a lot of details about controlling colour in the docs, and even font size, but nothing about the box sizes.