title: Max value for a Multi-key Hash
body: <p>This is my Hash (in Json)
  I need to get the Maximum value of each "high" value. For example, in this case is 16.94</p>
  
  <p>How to get this in Ruby?</p>
  
  <p>I tried with [].max function, but i don't know to set the "key" where valutate the max</p>
  
  <pre><code>{
   "query": {
    "count": 124,
    "created": "2012-03-21T20:45:39Z",
    "lang": "en-US",
    "results": {
     "quote": [
      {
       "date": "2010-03-10",
       "Date": "2010-03-10",
       "Open": "16.51",
       "High": "16.94",
       "Low": "16.51",
       "Close": "16.79",
       "Volume": "33088600",
       "Adj_Close": "16.79"
      },
      {
       "date": "2010-03-09",
       "Date": "2010-03-09",
       "Open": "16.41",
       "High": "16.72",
       "Low": "16.40",
       "Close": "16.53",
       "Volume": "20755200",
       "Adj_Close": "16.53"
      },
      {
       "date": "2010-03-08",
       "Date": "2010-03-08",
       "Open": "16.32",
       "High": "16.61",
       "Low": "16.30",
       "Close": "16.52",
       "Volume": "30554000",
       "Adj_Close": "16.52"
      },
      {
       "date": "2010-03-05",
       "Date": "2010-03-05",
       "Open": "15.89",
       "High": "16.38",
       "Low": "15.89",
       "Close": "16.06",
       "Volume": "21415000",
       "Adj_Close": "16.06"
      }
  </code></pre>