Texas Estates Code - EST § 256.154. Proof of Execution of Holographic Will

(a) A will wholly in the handwriting of the testator that is not self-proved as provided by this title may be proved by two witnesses to the testator's handwriting.  The evidence may be by:

(b) A witness being deposed for purposes of proving the will as provided by Subsection (a)(2) may testify by referring to a certified copy of the will, without the judge requiring the original will to be removed from the court's file and shown to the witness.