Posts have better shear resistance set in concrete or with shear resistant brackets. 1 ton is quite a lot of concentrated point load in a hoist system. It's very important to ensure that the brackets connecting that to the lumber distribute the load properly and are arranged with through bolting instead of lag bolting and without an excess amount of wood drilled out to provide adequate load transfer. In addition to that the right amount of wood cross joists and beams or truss system to transfer that load is very important.

Lifting heavy things overhead is a life safety application so it would be very wise to collaborate with a PE in your area to get stamped drawings calculated with an appropriate safety factor for variability and glitches that happen in lumber based construction because a failure could cause serious negative consequences for life or property.

4x4 posts won't really offer the best shear resistance because they will tend to deflect easily under heavy compression. It would be wise to figure out how to cross brace all the posts to their neighbors to increase stiffness.