Is there a way to limit the number of emails sent per day from a Canvas?

This is how I have done it: 

1. Create a segment of Gmail users using regex: Email matches regex /^@gmail\.com$/ 
2. Set up a decision split in your canvas to filter out Gmail users
3. Use an Experiment Path to assign % of users to receive the emails. For example, if your audience is 100, 1% = 1 email send. Start with 1%, and then 5%, ramping up gradually
4. You can use delay steps to limit the sends per day. For example Path 1 will send immediately, Path 2 +1 Calendar Day, etc

Hope this helps