gistfile1.html

<form action="/payment" method="POST">
      <!-- identification -->
      <input name="order[user_id]" type="text" value="6" />

      <!-- order -->
      <input name="order[number]" type="input" value="777" />
      <input name="order[email]" type="input" value="coon@example.com" />
      <input name="order[total_amount]" type="input" value="2500" />
      <input name="order[currency]" type="input" value="USD" />

      <!-- item -->
      <input name="order[line_items_attributes][][name]" type="input" value="Pragmatic Development Book" />
      <input name="order[line_items_attributes][][amount]" type="input" value="1500" />
      <input name="order[line_items_attributes][][quantity]" type="input" value="1" />
      <input name="order[line_items_attributes][][number]" type="input" value="1" />

      <!-- item -->
      <input name="order[line_items_attributes][][name]" type="input" value="Pragmatic Integration Book" />
      <input name="order[line_items_attributes][][amount]" type="input" value="1000" />
      <input name="order[line_items_attributes][][quantity]" type="input" value="1" />
      <input name="order[line_items_attributes][][number]" type="input" value="2" />

      <input type="submit" value="Pay"/>
</form>