If you just see a blank page or get a jquery-1.7 error

[johannesE]

Then this might help:
As previously mentioned here, mercury needs jquery 1.7 to work and includes it already. So if you get this error:
Asset filtered out and will not be served: add Rails.application.config.assets.precompile += %w( jquery-1.7.js ) to config/initializers/assets.rb and restart your server
Do not just remove the <%= javascript_include_tag 'jquery-1.7', 'mercury' %>, but rather do what the bug says.
If this helps lots of users, something like this might get added into the readme.md?

I had this under rails 4 with jquery-rails (comes in version 1.11.1 already).