light as a feather
Extremely lightweight. This simile can be used to refer either to physical weight, as in This load is light as a feather, or to texture, as in This cake is light as a feather. [Mid-1500s]
The American Heritage® Idioms Dictionary Copyright © 2002, 2001, 1995 by Houghton Mifflin Harcourt Publishing Company. Published by Houghton Mifflin Harcourt Publishing Company.