He brought a new earthenware cup and put half a log of water from the kiyor into it; R’ Yehudah says: A quarter [of a log]. Just as he minimizes the [amount of] writing [required], so too he minimizes the [amount of] water [required].  He entered the Sanctuary and turned to his right —- where there was a spot one cubit by one cubit with a marble flagstone with a ring fixed in it; and when he raised it, he took dust from beneath it. He added enough to be visible on the water, as it is stated (v. 17): And the Kohen shall take from the dust that will be on the Tabernacle floor and add it to the water.