Tosefta for Pesachim 128:13

One time King [Herod] Agrippa sought to find out how many were the multitudes [of Israelites], and he said to the Kohanim, separate for me a kidney from each and every Passover offering, and they separated for him six hundred thousand pairs of kidneys, double the number of the exodus from Egypt, and there was not any Passover offering that did not have at least ten registrants, not including those who [could not attend because they] were impure or that had too long of a distance to travel. On that day, they entered the Temple Mount and it could not hold all of them, and they called it the "Passover of the crushed."