as stated in
“The process of making ice in the East Indies at Allahabad, Mootegil, and Calcutta”.
On a large open plain, three or four excavations were made, the bottoms of which were sugar-cane, or the stems of the large Indian corn dried. Upon this bed were placed in rows, a number of small, shallow, earthen pans, for containing the water intended to be frozen. These are unglazed, and made of a prous Earth. Towards the dusk of the evening, they were filled with soft water, which had been boiled, and then left in the afore-related situation.
The ice-makers attended the pits usually before the sun was above the horizon, and collected in baskets what was frozen.