> db.messages.aggregate( [     {$project: {             "headers.Mime-Version":1,             _id:0         }     }, {$limit: 0} ])
assert: command failed: { "ok" : 0, "errmsg" : "unrecognized field \"cursor" } : aggregate with cursor failed
Error: Printing Stack Trace
    at printStackTrace (src/mongo/shell/utils.js:38:15)
    at doassert (src/mongo/shell/assert.js:6:5)
    at Function.assert.commandWorked (src/mongo/shell/assert.js:238:5)
    at DBCollection.aggregate (src/mongo/shell/collection.js:907:12)
    at (shell):1:13
2013-10-16T14:33:44.254-0700 command failed: { "ok" : 0, "errmsg" : "unrecognized field \"cursor" } : aggregate with cursor failed at src/mongo/shell/assert.js:7
>