Different wood species have different weights per cubic inch; same wood species from same log, same layer (further along the length) and same dimension could vary due to moisture content; and heartwood weighs more than the outer sections owing to density due to shrinkage and compaction of the cells. Here is link that illustrates. If you are concerned, a cheap digital scale may help as will a moisture meter. I have both but rarely use either.
https://www.arborday.org/trees/RingsTreeNatomy.cfm