Mongoose: Multiple 3 Level Deep Population

Question

I have the following schemas:

var userSchema = new Schema({
    username: String,
    rooms: [{type: Schema.Types.ObjectId, ref: 'Room'}]
});

var roomSchema = new Schema({
    members: [
            {
                user:{type:Schema.Types.ObjectId, ref 'User'},
                role: String
            }
        ],
    messages: [
            {
                text: String,
                meta: {
                    send: {type: Schema.Types.ObjectId, ref 'User'},
                    sent_time: Date
                }
            }
        ]
});

I wish to obtain all rooms of a particular user and deep populate each room to get populated messages and members arrays so that each sender in a message is populated with username and each member is populated with his/her username, something like this:

User.findById(id).
populate({
    path: 'rooms',
    populate: [
        {
            path: 'members.user',
            select: 'username'
        },
        {
            path:  'messages.meta.sender',
            select: 'username'
        }
    ]
}).exec(function(err, self) { // self becomes deep populated});

Obviously, the above didn't work for me.