What is the water filter of Koṇāgamana?

No matter how many different ways I search, I seem to get this exact/ALMOST exact phrase:"These relics include the staff of Kakusandha, the water filter of Koṇāgamana, a piece of the robe of Kassapa, and eight strands of hair from the ..." But I cannot find an explanation for it. This supposedly belonged to the "grandfather" Buddha to Gautama, aka Koṇāgamana (all according to https://en.wikipedia.org/wiki/List_of_the_named_Buddhas) , and Siddhartha supposedly lived in the 6th century BCE. If there are 1,000 Buddhas per *kalpa* and 4.32 billion years in a *kalpa*, that means they average 4.32 million years between appearances. So, what could this "water filter" possibly consist of? Thank you for your input. To be specific, I am interested in the history and historicity of this artifact. For example, when was it first mentioned? From where did it originate? How did it come to Shewdagon Pagoda? Etc...