Error_page with try_files

Server NGINX
1

I want to check if the user has a custom error page, if not shows a
default inside nginx basedir.

error_page 404 403 502 503 504 = @error;

location @error {
  try_files /404.htm /404.html /404.php (how to point to a file

outside document root?);
}

Marcos N.
+55 44 9918-8488