knockout.js foreach内でforeachをする

▼下記のようなデータ
ary[0][0] = {"day": 0, "num": 1};
ary[0][1] = {"day": 1, "num": 2};
ary[0][2] = {"day": 2, "num": 3};
ary[0][3] = {"day": 3, "num": 4};
ary[1][0] = {"day": 4, "num": 1};
ary[1][1] = {"day": 5, "num": 2};
ary[1][2] = {"day": 6, "num": 3};
ary[1][3] = {"day": 7, "num": 4};

▼下記のような記述
<table>
<tbody data-bind="foreach: ary()">
<tr data-bind="foreach: $data">
<td data-bind="text: day"></td>
</tr>
</tbody>
</table>