Agniveshyagrihyasutra 3.6.3.16

3.6.3.16

athainam aparimitaiḥ kṣudramiśrairaśmabhiḥ paricinoti na tena paricinuyād yathāsya kapotaḥ chāyāyāmupaviśet \

Then she piles around it with an unmeasured number of small stones mixed together; she should not pile around it in such a way that a pigeon would sit in its shade.