Updated as of April 1st, 2011
Updated as of July 27th, 2012
From Exalted Wiki
These discs can adhere to an inanimate object and reduce its weight. It isn't possible to make an object completely weightless.There are Artifact ●● versions that cost 5 motes to commit, and can make objects of less than a certain size weightless. Someone can use multiple discs to make larger objects weightless.
Source: Wonders of the Lost Age, p. 58