Android : How to set default typeface of Android WebView

How to set default typeface of a WebView in Android?

I know, I can use CSS fonts, But how can I use it when I want to show an external URL like http://HossainCo.ir

For example, In dekstop firefox (currently I used) we can set default font to use when no other fonts used in CSS or HTML

So: I want to use "assets" font like "fonts/tohoma.ttf" when using webView.loadUrl("hossainco.ir");