tested on jruby 1.6

mongoid_1_1.rb

require 'rubygems'
require 'mongoid'

class Coach  
  include Mongoid::Document 
  field :name, :type => String 
  belongs_to :coached, :class_name => 'Team', :inverse_of => :coach, :foreign_key => "coach_id" 
  belongs_to :assisted, :class_name => 'Team', :inverse_of => :assist, :foreign_key => "assist_id" 
end 

class Team 
  include Mongoid::Document 
  field :name, :type => String 
  has_one :coach, :class_name => 'Coach', :inverse_of => :coached 
  has_one :assist, :class_name => 'Coach', :inverse_of => :assisted 
end 

c = Coach.new(:name => "Tom")
a = Coach.new(:name => "Dick") 
t = Team.new(:name => "Allstars") 
t.coach = c
t.assist = a
c.coached = t

p c
p c.coached.assist.assisted