1994, New Scientist, Volume 144, Issues 1951-1958, page 81:
one Earth mass is now simply 5977 yottagrams (Yg), and the planets can be measured in Yg and moons in zettagrams (Zg).
2009 December 16, "Buddenbrooks" <knightstemplar@budweiser.com>, “Re: The definitive CO2 thread....”, in uk.business.agriculture[1] (Usenet), retrieved 2011-10-16, message-ID <X2aWm.60285$O74.46102@newsfe25.ams2>:
The atmosphere has a mass of about five zettagrams (5x1018kg or 5 pentatonnes).