Passing value from one page to Action:Mailer

I am a newbie to RoR, but love it.

Quick question:
I want to pass a value from one object to the Action:Mailer email form.
For example, I am on an “investment detail” page. I created a button to
send email from this page to the email form. However, how do I pass
values from the investment object to the Action:Mailer form?