Don't do:

temperature: {
  _id: 42,
  points: [
    { 1332942067: 17.3 },
    { 1332942118: 17.5 },
  ]
}

Instead, do:

temperature: {
  _id: 42,
  points: [
    { ts: 1332942067, temp: 17.3 },
    { ts: 1332942118, temp: 17.5 },
  ]
}

Define and document your keys!