Setting default headers in Rails3 applications

I know that you can set default headers application wide in config/application.rb for Rails4+ apps but what is the accepted method in older versions of Rails, as in Rails3?

At the moment I am setting them in application_controller.rb as a before_filter method, but I think this is a bad practices and performance -impacting

https://edgeguides.rubyonrails.org/security.html?utm_source=twitterfeed&utm_medium=twitter#default-headers