hashcash-path

hashcash-path is a variable defined in `hashcash.el'.
Its value is

"hashcash"

• This variable is an alias for `hashcash-program'.
• This variable is obsolete since 24.4;
  use `hashcash-program' instead.
• This variable may be risky if used as a file-local variable.

Documentation:
The name of the hashcash executable.
If this is not in your PATH, specify an absolute file name.

You can customize this variable.