How does one use a literal {{ in a Mustache template?

You can use {{ by itself quite easily. If you are trying to document something like {{example}} you could always pass in the first two cur lies with your data.

orphaned curlies are easy {{ <br>
{{curly}}example}} curlies are harder

Some simple rendering:

var data = { 'curly' : '{{'},
    tpl = $('#curly').html(),
    html = Mustache.to_html(tpl, data);

document.write(html);​

Results in:

orphaned curlies are easy {{ 
{{example}} curlies are harder

Here's the full working jsFiddle

Just change the delimiters temporarily:

{{=<% %>=}}
{{Look at the curlies!}}
<%={{ }}=%>

Assuming you are outputting HTML you could use an HTML entity to avoid it (mustache doesn't have any way to escape the opening tag built in).

So to output {{ you would write {{.
To output <% you would write <%.