Cast beyond the Moon
To form wild conjectures. One of Heywood's proverbs. At one time the moon was supposed to influence the weather, to affect the ingathering of fruits, to rule the time of sowing, reaping, and slaying cattle, etc.
“I talke of things impossible, and cast beyond the moon.” Heywood.
Source: Dictionary of Phrase and Fable, E. Cobham Brewer, 1894