The lowest EMB/BTC could go was 1 satoshi, but the real price was like a quarter or a tenth of a satoshi.
For that reason some exchanges introduced another zero, making 0.1 Satoshi trades possible. I think Novaexchange and Coinsmarkets are 2 of them. Others introduced alternative trading currencies in parallel to BTC. Yobit and already mentioned Cryptopia have done that. There is however usually a minimal trading volume, to discourage such 0.1 Satoshi transactions. Yobit has a minimum value of 10 Doge per trade, I think that is as low as it gets.