How do I update an item in an array in this document structure?
===

I have the following document structure:

    {
      "_id" : "20120725/foobar/song/test-pg3-long-title-here-test-lorem-ipsum-dolor-lo",
      "live_daily_count" : 4,
      "metacontent" : { "date" : "20120725",
        "live_daily_statable_slug" : "test-pg3-long-title-here-test-lorem-ipsum-dolor-lo",
        "live_daily_statable_title" : "test pg3 long title here test lorem ipsum dolor lorem ipsume dolor long description here msam dfam sdfm asfa sfasfas df as f as fas f sa f",
        "live_daily_statable_type" : "Song",
        "url" : "foobar/songs/test-pg3-long-title-here-test-lorem-ipsum-dolor-lo",
        "user_slug" : "foobar" },
      "visits" : [
        { "country_name" : "UK",
          "iso_two_letter_country_code" : "UK",
          "referer" : "http://localhost:3000/",
          "minute" : 1121,
          "token_id" : "13432416893tlfsmmgh" },
        { "country_name" : "UK",
          "iso_two_letter_country_code" : "UK",
          "referer" : "http://localhost:3000/",
          "minute" : 1281,
          "token_id" : "13432512733xcqhhrqs" },
        { "country_name" : "UK",
          "iso_two_letter_country_code" : "UK",
          "referer" : "http://localhost:3000/",
          "minute" : 1285,
          "token_id" : "13432515303rwiaczcx" },
        { "country_name" : "UK",
          "iso_two_letter_country_code" : "UK",
          "referer" : "http://localhost:3000/",
          "minute" : 1288,
          "token_id" : "13432517303eusgjcgz" }
      ]
    }

How do I find the visit with `token_id` `13432515303rwiaczcx` and update its `minute` to 1234?

I am able to `find` the item in the array using the Aggregation Framework (code below), but how do I update it?

      connection = Mongo::Connection.new
      database   = conn['foobar_development']

      query = {
        aggregate: 'live_daily_stats',
        pipeline: [
          { '$project' => {
            :visits => 1,
          } },
          { '$unwind' => '$visits' },
          { '$match' => { 'visits.token_id' => '13432515303rwiaczcx' } },
        ]
      }

      visit = database.command(query)['result'][0][0]

Which returns:

    {
           "_id" => "20120725/foobar/song/test-pg3-long-title-here-test-lorem-ipsum-dolor-lo",
        "visits" => {
                                          "country_name" => "UK",
                           "iso_two_letter_country_code" => "UK",
                                               "referer" => "http://localhost:3000/",
                                                "minute" => 1285,
                                              "token_id" => "13432515303rwiaczcx"
        }
    }