(Ibid. 14) "and, behold, on the face of the desert": Not on the whole desert, but on part of it. (Ibid.) "thin as hoarfrost": We are hereby apprised that it descended like ice on the ground. These are the words of R. Yehoshua.
Second, Rabbi Joshua Explains the Phrase Thin as Hoarfrost to Mean
Mekhilta Tractate Vayassa 4:14