expression.rb

class Expression
  include Mongoid::Document

  field :english
end

index.mustache

<ul>
  {{#expressions}}
    {{#map}}
      <li>{{english}}</li>
    {{/map}}
    <br class="clear" />
  {{/expressions}}
</ul>

index.rb

class Index < Mustache
  def expressions
    results = Expression.where(some_conditions)
    results.in_groups_of(4)
  end
end